diff --git a/src/proto_alpha/bin_sc_rollup_node/injector.ml b/src/proto_alpha/bin_sc_rollup_node/injector.ml
index 982460e53953e6c87c7999ab26577bf922975ea7..f34cfe5bd865da12667c987fa9dbe1e0fb0997bf 100644
--- a/src/proto_alpha/bin_sc_rollup_node/injector.ml
+++ b/src/proto_alpha/bin_sc_rollup_node/injector.ml
@@ -90,7 +90,7 @@ module Parameters :
   let approximate_fee_bound _ _ =
     {
       fee = Tez.of_mutez_exn 3_000_000L;
-      counter = Z.of_int 500_000;
+      counter = Manager_counter.Internal_for_tests.of_int 500_000;
       gas_limit = Gas.Arith.integral_of_int_exn 500_000;
       storage_limit = Z.of_int 500_000;
     }
diff --git a/src/proto_alpha/lib_client/annotated_manager_operation.ml b/src/proto_alpha/lib_client/annotated_manager_operation.ml
index 96ce163f52957835a010ef593dddd41328fb771b..7aa1a7fc7080f5db712e83aa87aa7dfd45e9edb3 100644
--- a/src/proto_alpha/lib_client/annotated_manager_operation.ml
+++ b/src/proto_alpha/lib_client/annotated_manager_operation.ml
@@ -33,7 +33,7 @@ type _ t =
       fee : Tez.t Limit.t;
       gas_limit : Gas.Arith.integral Limit.t;
       storage_limit : Z.t Limit.t;
-      counter : Z.t option;
+      counter : Manager_counter.t option;
       operation : 'kind manager_operation;
     }
       -> 'kind t
diff --git a/src/proto_alpha/lib_client/annotated_manager_operation.mli b/src/proto_alpha/lib_client/annotated_manager_operation.mli
index 4eebe07b7a599a6ee581323022e4a1652d23a9d1..0fc7a472f84216d878749fbc2f5192edc543be77 100644
--- a/src/proto_alpha/lib_client/annotated_manager_operation.mli
+++ b/src/proto_alpha/lib_client/annotated_manager_operation.mli
@@ -36,7 +36,7 @@ type _ t =
       fee : Tez.t Limit.t;
       gas_limit : Gas.Arith.integral Limit.t;
       storage_limit : Z.t Limit.t;
-      counter : Z.t option;
+      counter : Manager_counter.t option;
       operation : 'kind manager_operation;
     }
       -> 'kind t
@@ -85,7 +85,7 @@ val set_storage_limit : Z.t Limit.t -> 'a t -> 'a t
 
 (** Set the counter of the annotated operation. Fail if the counter
     is already set. *)
-val set_counter : counter -> 'a t -> 'a t tzresult
+val set_counter : Manager_counter.t -> 'a t -> 'a t tzresult
 
 (** Set the source of the operation. Fail if the source is already set. *)
 val set_source : public_key_hash -> 'a t -> 'a t tzresult
diff --git a/src/proto_alpha/lib_client/client_proto_args.ml b/src/proto_alpha/lib_client/client_proto_args.ml
index 416901802ab023335980b0a97a31506747faa814..068a034119df0f78f20a0501933767ec2b9ba5c2 100644
--- a/src/proto_alpha/lib_client/client_proto_args.ml
+++ b/src/proto_alpha/lib_client/client_proto_args.ml
@@ -313,6 +313,12 @@ let non_negative_z_parameter =
 let non_negative_z_param ~name ~desc next =
   Tezos_clic.param ~name ~desc non_negative_z_parameter next
 
+let counter_parameter =
+  Tezos_clic.parameter (fun _ s ->
+      match Manager_counter.Internal_for_injection.of_string s with
+      | None -> failwith "Invalid counter, must be a non-negative number."
+      | Some c -> return c)
+
 let non_negative_parameter =
   Tezos_clic.parameter (fun _ s ->
       match int_of_string_opt s with
@@ -450,7 +456,7 @@ let counter_arg =
     ~short:'C'
     ~placeholder:"counter"
     ~doc:"Set the counter to be used by the transaction"
-    non_negative_z_parameter
+    counter_parameter
 
 let max_priority_arg =
   Tezos_clic.arg
diff --git a/src/proto_alpha/lib_client/client_proto_args.mli b/src/proto_alpha/lib_client/client_proto_args.mli
index c0a0f0a488abcb6038b043e30f024f943964c62a..79ffb850794016f17d74573d23bcce03bec9eacb 100644
--- a/src/proto_alpha/lib_client/client_proto_args.mli
+++ b/src/proto_alpha/lib_client/client_proto_args.mli
@@ -36,7 +36,7 @@ val fee_arg : (Tez.t option, full) Tezos_clic.arg
 
 val default_fee_arg : (Tez.t option, full) Tezos_clic.arg
 
-val counter_arg : (Z.t option, full) Tezos_clic.arg
+val counter_arg : (Manager_counter.t option, full) Tezos_clic.arg
 
 val gas_limit_arg : (Gas.Arith.integral option, full) Tezos_clic.arg
 
diff --git a/src/proto_alpha/lib_client/client_proto_context.mli b/src/proto_alpha/lib_client/client_proto_context.mli
index e25b0a0aa97a584207e42524a9eb1a89fd7648af..17e25123bc716f639cd9d955c90100f96110122e 100644
--- a/src/proto_alpha/lib_client/client_proto_context.mli
+++ b/src/proto_alpha/lib_client/client_proto_context.mli
@@ -80,7 +80,7 @@ val register_global_constant :
   ?fee:Tez.tez ->
   ?gas_limit:Gas.Arith.integral ->
   ?storage_limit:Z.t ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   source:Signature.public_key_hash ->
   src_pk:Signature.public_key ->
   src_sk:Client_keys.sk_uri ->
@@ -336,7 +336,7 @@ val transfer_with_script :
   ?fee:Tez.t ->
   ?gas_limit:Gas.Arith.integral ->
   ?storage_limit:Z.t ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   fee_parameter:Injection.fee_parameter ->
   ?replace_by_fees:bool ->
   unit ->
@@ -370,7 +370,7 @@ val transfer :
   ?fee:Tez.t ->
   ?gas_limit:Gas.Arith.integral ->
   ?storage_limit:Z.t ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   fee_parameter:Injection.fee_parameter ->
   ?replace_by_fees:bool ->
   unit ->
@@ -580,7 +580,7 @@ val originate_tx_rollup :
   ?fee:Tez.tez ->
   ?gas_limit:Gas.Arith.integral ->
   ?storage_limit:Z.t ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   source:Signature.public_key_hash ->
   src_pk:Signature.public_key ->
   src_sk:Client_keys.sk_uri ->
@@ -604,7 +604,7 @@ val submit_tx_rollup_batch :
   ?burn_limit:Tez.tez ->
   ?gas_limit:Gas.Arith.integral ->
   ?storage_limit:Z.t ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   source:Signature.public_key_hash ->
   src_pk:Signature.public_key ->
   src_sk:Client_keys.sk_uri ->
@@ -629,7 +629,7 @@ val submit_tx_rollup_commitment :
   ?fee:Tez.tez ->
   ?gas_limit:Gas.Arith.integral ->
   ?storage_limit:Z.t ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   source:Signature.public_key_hash ->
   src_pk:Signature.public_key ->
   src_sk:Client_keys.sk_uri ->
@@ -657,7 +657,7 @@ val submit_tx_rollup_finalize_commitment :
   ?fee:Tez.tez ->
   ?gas_limit:Gas.Arith.integral ->
   ?storage_limit:Z.t ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   source:Signature.public_key_hash ->
   src_pk:Signature.public_key ->
   src_sk:Client_keys.sk_uri ->
@@ -682,7 +682,7 @@ val submit_tx_rollup_remove_commitment :
   ?fee:Tez.tez ->
   ?gas_limit:Gas.Arith.integral ->
   ?storage_limit:Z.t ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   source:Signature.public_key_hash ->
   src_pk:Signature.public_key ->
   src_sk:Client_keys.sk_uri ->
@@ -706,7 +706,7 @@ val submit_tx_rollup_rejection :
   ?fee:Tez.tez ->
   ?gas_limit:Gas.Arith.integral ->
   ?storage_limit:Z.t ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   source:Signature.public_key_hash ->
   src_pk:Signature.public_key ->
   src_sk:Client_keys.sk_uri ->
@@ -740,7 +740,7 @@ val submit_tx_rollup_return_bond :
   ?fee:Tez.tez ->
   ?gas_limit:Gas.Arith.integral ->
   ?storage_limit:Z.t ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   source:Signature.public_key_hash ->
   src_pk:Signature.public_key ->
   src_sk:Client_keys.sk_uri ->
@@ -764,7 +764,7 @@ val tx_rollup_dispatch_tickets :
   ?fee:Tez.tez ->
   ?gas_limit:Gas.Arith.integral ->
   ?storage_limit:Z.t ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   source:Signature.public_key_hash ->
   src_pk:Signature.public_key ->
   src_sk:Client_keys.sk_uri ->
@@ -793,7 +793,7 @@ val transfer_ticket :
   ?fee:Tez.tez ->
   ?gas_limit:Gas.Arith.integral ->
   ?storage_limit:Z.t ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   source:Signature.public_key_hash ->
   src_pk:Signature.public_key ->
   src_sk:Client_keys.sk_uri ->
@@ -822,7 +822,7 @@ val sc_rollup_originate :
   ?fee:Tez.t ->
   ?gas_limit:Gas.Arith.integral ->
   ?storage_limit:Z.t ->
-  ?counter:counter ->
+  ?counter:Manager_counter.t ->
   source:public_key_hash ->
   kind:Sc_rollup.Kind.t ->
   boot_sector:string ->
@@ -849,7 +849,7 @@ val sc_rollup_add_messages :
   ?fee:Tez.t ->
   ?gas_limit:Gas.Arith.integral ->
   ?storage_limit:Z.t ->
-  ?counter:counter ->
+  ?counter:Manager_counter.t ->
   source:public_key_hash ->
   messages:string list ->
   src_pk:public_key ->
@@ -873,7 +873,7 @@ val sc_rollup_cement :
   ?fee:Tez.t ->
   ?gas_limit:Gas.Arith.integral ->
   ?storage_limit:Z.t ->
-  ?counter:counter ->
+  ?counter:Manager_counter.t ->
   source:public_key_hash ->
   rollup:Alpha_context.Sc_rollup.t ->
   commitment:Alpha_context.Sc_rollup.Commitment.Hash.t ->
@@ -898,7 +898,7 @@ val sc_rollup_publish :
   ?fee:Tez.t ->
   ?gas_limit:Gas.Arith.integral ->
   ?storage_limit:Z.t ->
-  ?counter:counter ->
+  ?counter:Manager_counter.t ->
   source:public_key_hash ->
   rollup:Alpha_context.Sc_rollup.t ->
   commitment:Alpha_context.Sc_rollup.Commitment.t ->
@@ -923,7 +923,7 @@ val sc_rollup_execute_outbox_message :
   ?fee:Tez.t ->
   ?gas_limit:Gas.Arith.integral ->
   ?storage_limit:Z.t ->
-  ?counter:counter ->
+  ?counter:Manager_counter.t ->
   source:public_key_hash ->
   rollup:Sc_rollup.t ->
   cemented_commitment:Sc_rollup.Commitment.Hash.t ->
@@ -951,7 +951,7 @@ val sc_rollup_recover_bond :
   ?fee:Tez.tez ->
   ?gas_limit:Gas.Arith.integral ->
   ?storage_limit:Z.t ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   source:Signature.public_key_hash ->
   src_pk:Signature.public_key ->
   src_sk:Client_keys.sk_uri ->
@@ -975,7 +975,7 @@ val sc_rollup_refute :
   ?fee:Tez.t ->
   ?gas_limit:Gas.Arith.integral ->
   ?storage_limit:Z.t ->
-  ?counter:counter ->
+  ?counter:Manager_counter.t ->
   source:public_key_hash ->
   rollup:Alpha_context.Sc_rollup.t ->
   refutation:Alpha_context.Sc_rollup.Game.refutation option ->
@@ -1001,7 +1001,7 @@ val sc_rollup_timeout :
   ?fee:Tez.t ->
   ?gas_limit:Gas.Arith.integral ->
   ?storage_limit:Z.t ->
-  ?counter:counter ->
+  ?counter:Manager_counter.t ->
   source:public_key_hash ->
   rollup:Alpha_context.Sc_rollup.t ->
   alice:Alpha_context.Sc_rollup.Staker.t ->
@@ -1027,7 +1027,7 @@ val sc_rollup_dal_slot_subscribe :
   ?fee:Tez.t ->
   ?gas_limit:Gas.Arith.integral ->
   ?storage_limit:Z.t ->
-  ?counter:counter ->
+  ?counter:Manager_counter.t ->
   source:public_key_hash ->
   rollup:Alpha_context.Sc_rollup.t ->
   slot_index:int ->
diff --git a/src/proto_alpha/lib_client/client_proto_fa12.mli b/src/proto_alpha/lib_client/client_proto_fa12.mli
index 14f56e24cb57949700e4f3de1727e80722d5b98b..cfd100f44a46010c0ae3f41c03fd67493bec7ed4 100644
--- a/src/proto_alpha/lib_client/client_proto_fa12.mli
+++ b/src/proto_alpha/lib_client/client_proto_fa12.mli
@@ -106,7 +106,7 @@ val call_contract :
   ?fee:Tez.t ->
   ?gas_limit:Gas.Arith.integral ->
   ?storage_limit:Z.t ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   fee_parameter:Injection.fee_parameter ->
   unit ->
   (Kind.transaction Kind.manager Injection.result * Contract_hash.t list)
@@ -140,7 +140,7 @@ val inject_token_transfer_batch :
   src_sk:Client_keys.sk_uri ->
   token_transfers:token_transfer list ->
   fee_parameter:Injection.fee_parameter ->
-  ?counter:counter ->
+  ?counter:Manager_counter.t ->
   ?default_fee:Tez.t ->
   ?default_gas_limit:Gas.Arith.integral ->
   ?default_storage_limit:Z.t ->
diff --git a/src/proto_alpha/lib_client/client_proto_multisig.mli b/src/proto_alpha/lib_client/client_proto_multisig.mli
index bd2f3d746552f6a392a419a1654013952d0417b7..5ebfd1448d0fe6c47ff0f8fc30c943acc51e2c5a 100644
--- a/src/proto_alpha/lib_client/client_proto_multisig.mli
+++ b/src/proto_alpha/lib_client/client_proto_multisig.mli
@@ -117,7 +117,7 @@ val call_multisig :
   ?fee:Tez.t ->
   ?gas_limit:Gas.Arith.integral ->
   ?storage_limit:Z.t ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   fee_parameter:Injection.fee_parameter ->
   unit ->
   (Kind.transaction Kind.manager Injection.result * Contract_hash.t list)
@@ -144,7 +144,7 @@ val call_multisig_on_bytes :
   ?fee:Tez.t ->
   ?gas_limit:Gas.Arith.integral ->
   ?storage_limit:Z.t ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   fee_parameter:Injection.fee_parameter ->
   unit ->
   (Kind.transaction Kind.manager Injection.result * Contract_hash.t list)
diff --git a/src/proto_alpha/lib_client/injection.ml b/src/proto_alpha/lib_client/injection.ml
index bec0a611639205922f1063c497241756ab86c71a..a05bf5079bdaeb38efe4df1580140b2656813e02 100644
--- a/src/proto_alpha/lib_client/injection.ml
+++ b/src/proto_alpha/lib_client/injection.ml
@@ -1375,7 +1375,7 @@ let inject_manager_operation cctxt ~chain ~block ?successor_level ?branch
   | None ->
       Alpha_services.Contract.counter cctxt (chain, block) source
       >>=? fun pcounter ->
-      let counter = Z.succ pcounter in
+      let counter = Manager_counter.succ pcounter in
       return counter
   | Some counter -> return counter)
   >>=? fun counter ->
@@ -1398,7 +1398,7 @@ let inject_manager_operation cctxt ~chain ~block ?successor_level ?branch
   in
   let rec build_contents :
       type kind.
-      Z.t ->
+      Manager_counter.t ->
       kind Annotated_manager_operation.annotated_list ->
       kind Annotated_manager_operation.annotated_list tzresult =
    fun counter -> function
@@ -1407,7 +1407,7 @@ let inject_manager_operation cctxt ~chain ~block ?successor_level ?branch
         Annotated_manager_operation.Single_manager op
     | Cons_manager (op, rest) ->
         apply_specified_options counter op >>? fun op ->
-        build_contents (Z.succ counter) rest >|? fun rest ->
+        build_contents (Manager_counter.succ counter) rest >|? fun rest ->
         Annotated_manager_operation.Cons_manager (op, rest)
   in
   match key with
@@ -1425,7 +1425,7 @@ let inject_manager_operation cctxt ~chain ~block ?successor_level ?branch
       in
       Annotated_manager_operation.set_source source reveal >>?= fun reveal ->
       Annotated_manager_operation.set_counter counter reveal >>?= fun reveal ->
-      build_contents (Z.succ counter) operations >>?= fun rest ->
+      build_contents (Manager_counter.succ counter) operations >>?= fun rest ->
       let contents = Annotated_manager_operation.Cons_manager (reveal, rest) in
       may_patch_limits
         cctxt
diff --git a/src/proto_alpha/lib_client/injection.mli b/src/proto_alpha/lib_client/injection.mli
index 6275db8033e1c7d42abde993696a628f0461f4d3..d66775157c80a34c0ea1bc2469c28e4d062a5ef5 100644
--- a/src/proto_alpha/lib_client/injection.mli
+++ b/src/proto_alpha/lib_client/injection.mli
@@ -109,7 +109,7 @@ val inject_manager_operation :
   fee:Tez.t Limit.t ->
   gas_limit:Gas.Arith.integral Limit.t ->
   storage_limit:Z.t Limit.t ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   ?replace_by_fees:bool ->
   fee_parameter:fee_parameter ->
   'kind Annotated_manager_operation.annotated_list ->
diff --git a/src/proto_alpha/lib_client/managed_contract.mli b/src/proto_alpha/lib_client/managed_contract.mli
index aea7fb7763fd945af872ae222fee7871eee63852..b459230ae8b390e5c949fb3c022e005d04e40d85 100644
--- a/src/proto_alpha/lib_client/managed_contract.mli
+++ b/src/proto_alpha/lib_client/managed_contract.mli
@@ -114,7 +114,7 @@ val transfer :
   ?fee:Tez.t ->
   ?gas_limit:Gas.Arith.integral ->
   ?storage_limit:Z.t ->
-  ?counter:counter ->
+  ?counter:Manager_counter.t ->
   fee_parameter:Injection.fee_parameter ->
   unit ->
   (Kind.transaction Kind.manager Injection.result * Contract_hash.t list)
diff --git a/src/proto_alpha/lib_client/operation_result.ml b/src/proto_alpha/lib_client/operation_result.ml
index 0c95c2b04f098e2b34b188e3b608d306c70e6503..f0fc58ae69475812352895d429a65e53c829c26c 100644
--- a/src/proto_alpha/lib_client/operation_result.ml
+++ b/src/proto_alpha/lib_client/operation_result.ml
@@ -995,7 +995,7 @@ let pp_manager_operation_result ppf
   Format.fprintf ppf "@[<v 2>Manager signed operations:" ;
   Format.fprintf ppf "@,From: %a" Signature.Public_key_hash.pp source ;
   Format.fprintf ppf "@,Fee to the baker: %s%a" tez_sym Tez.pp fee ;
-  Format.fprintf ppf "@,Expected counter: %a" Z.pp_print counter ;
+  Format.fprintf ppf "@,Expected counter: %a" Manager_counter.pp counter ;
   Format.fprintf ppf "@,Gas limit: %a" Gas.Arith.pp_integral gas_limit ;
   Format.fprintf ppf "@,Storage limit: %a bytes" Z.pp_print storage_limit ;
   pp_balance_updates ppf balance_updates ;
diff --git a/src/proto_alpha/lib_client_commands/client_proto_stresstest_commands.ml b/src/proto_alpha/lib_client_commands/client_proto_stresstest_commands.ml
index 140d2ab47d8ad1e08e22b18d24678d5b5a7c4e7d..8b81d1661024b9ce2156c234b6aa4a3d31eb0d28 100644
--- a/src/proto_alpha/lib_client_commands/client_proto_stresstest_commands.ml
+++ b/src/proto_alpha/lib_client_commands/client_proto_stresstest_commands.ml
@@ -94,7 +94,7 @@ type transfer = {
   fee : Tez.t;
   gas_limit : Gas.Arith.integral;
   amount : Tez.t;
-  counter : Z.t option;
+  counter : Manager_counter.t option;
   fresh_dst : bool;
 }
 
@@ -570,8 +570,8 @@ let inject_transfer (cctxt : Protocol_client_context.full) parameters state
   in
   let*! r =
     if not already_revealed then
-      let reveal_counter = Z.succ current_counter in
-      let transf_counter = Z.succ reveal_counter in
+      let reveal_counter = Manager_counter.succ current_counter in
+      let transf_counter = Manager_counter.succ reveal_counter in
       let reveal =
         Manager_operation
           {
@@ -595,9 +595,9 @@ let inject_transfer (cctxt : Protocol_client_context.full) parameters state
               "injecting reveal+transfer from %a (counters=%a,%a) to %a"
               Signature.Public_key_hash.pp
               transfer.src.pkh
-              Z.pp_print
+              Manager_counter.pp
               reveal_counter
-              Z.pp_print
+              Manager_counter.pp
               transf_counter
               Contract.pp
               (destination_to_contract transfer.dst))
@@ -608,7 +608,7 @@ let inject_transfer (cctxt : Protocol_client_context.full) parameters state
          all the operations we injected. *)
       inject_contents cctxt state.target_block transfer.src.sk list
     else
-      let transf_counter = Z.succ current_counter in
+      let transf_counter = Manager_counter.succ current_counter in
       let manager_op =
         manager_op_of_transfer
           parameters
@@ -621,7 +621,7 @@ let inject_transfer (cctxt : Protocol_client_context.full) parameters state
               "injecting transfer from %a (counter=%a) to %a"
               Signature.Public_key_hash.pp
               transfer.src.pkh
-              Z.pp_print
+              Manager_counter.pp
               transf_counter
               Contract.pp
               (destination_to_contract transfer.dst))
@@ -1274,7 +1274,7 @@ let estimate_transaction_cost ?smart_contracts
   let* current_counter =
     Alpha_services.Contract.counter cctxt (chain, block) src.source.pkh
   in
-  let transf_counter = Z.succ current_counter in
+  let transf_counter = Manager_counter.succ current_counter in
   let transfer =
     {
       src = src.source;
diff --git a/src/proto_alpha/lib_delegate/operation_selection.ml b/src/proto_alpha/lib_delegate/operation_selection.ml
index a658661df026589db7ffb88d4b2b797ab9da7f68..9a4fbf4d0b92ed64ffd2016bea743c8cebfca75b 100644
--- a/src/proto_alpha/lib_delegate/operation_selection.ml
+++ b/src/proto_alpha/lib_delegate/operation_selection.ml
@@ -45,7 +45,7 @@ type prioritized_manager = {
   gas : Fixed_point_repr.integral_tag Gas.Arith.t;
   weight : Q.t;
   source : public_key_hash;
-  counter : counter;
+  counter : Manager_counter.t;
 }
 
 module PrioritizedManagerSet = Set.Make (struct
@@ -60,7 +60,7 @@ module PrioritizedManagerSet = Set.Make (struct
     let cmp_src = Signature.Public_key_hash.compare source source' in
     if cmp_src = 0 then
       (* we want the smallest counter first *)
-      let c = Z.compare counter counter' in
+      let c = Manager_counter.compare counter counter' in
       if c <> 0 then c
       else
         let c = Prioritized_operation.compare_priority op' op in
diff --git a/src/proto_alpha/lib_injector/injector_sigs.ml b/src/proto_alpha/lib_injector/injector_sigs.ml
index 29bd400af4065e0229e4e9d415ad3a07c8aeedcc..d9c56fda0736559cceb04078d5444cdb18be6d7a 100644
--- a/src/proto_alpha/lib_injector/injector_sigs.ml
+++ b/src/proto_alpha/lib_injector/injector_sigs.ml
@@ -29,7 +29,7 @@ open Protocol.Alpha_context
     to compute an upper bound on the size (in bytes) of an operation. *)
 type approximate_fee_bound = {
   fee : Tez.t;
-  counter : Z.t;
+  counter : Manager_counter.t;
   gas_limit : Gas.Arith.integral;
   storage_limit : Z.t;
 }
diff --git a/src/proto_alpha/lib_plugin/test/generators.ml b/src/proto_alpha/lib_plugin/test/generators.ml
index 014defb7a3660a06757100eede11ad60253e4552..afe935242a1ba02da6463c00c0e821aa9c68aeba 100644
--- a/src/proto_alpha/lib_plugin/test/generators.ml
+++ b/src/proto_alpha/lib_plugin/test/generators.ml
@@ -48,7 +48,7 @@ let dummy_manager_op_info =
   let manager_op =
     let open Alpha_context in
     let source = Signature.Public_key_hash.zero in
-    let counter = Z.zero in
+    let counter = Manager_counter.Internal_for_tests.of_int 0 in
     let storage_limit = Z.zero in
     let operation = Set_deposits_limit None in
     let contents =
diff --git a/src/proto_alpha/lib_protocol/TEZOS_PROTOCOL b/src/proto_alpha/lib_protocol/TEZOS_PROTOCOL
index 00bf18b7e7e791eb3b387d230d96de3041625e28..fb3eb85045a76f3b58563d1465a5f71a38a3b083 100644
--- a/src/proto_alpha/lib_protocol/TEZOS_PROTOCOL
+++ b/src/proto_alpha/lib_protocol/TEZOS_PROTOCOL
@@ -44,6 +44,7 @@
         "Sampler",
         "Voting_period_repr",
         "Ticket_hash_repr",
+        "Manager_counter_repr",
         "Contract_repr",
         "Indexable",
         "Entrypoint_repr",
diff --git a/src/proto_alpha/lib_protocol/alpha_context.ml b/src/proto_alpha/lib_protocol/alpha_context.ml
index 40e163c86ab0f4f6914d18953c1290df0406f777..6403ff9bd3cf95dfac39c966ed09295832bde693 100644
--- a/src/proto_alpha/lib_protocol/alpha_context.ml
+++ b/src/proto_alpha/lib_protocol/alpha_context.ml
@@ -140,6 +140,7 @@ module Zk_rollup = struct
 end
 
 module Entrypoint = Entrypoint_repr
+module Manager_counter = Manager_counter_repr
 include Operation_repr
 
 module Operation = struct
diff --git a/src/proto_alpha/lib_protocol/alpha_context.mli b/src/proto_alpha/lib_protocol/alpha_context.mli
index ef244db926944a80f352f4f3608589fbcdff7430..02aa58e382f50e2501f4735f4528c597b63a29ba 100644
--- a/src/proto_alpha/lib_protocol/alpha_context.mli
+++ b/src/proto_alpha/lib_protocol/alpha_context.mli
@@ -1597,6 +1597,29 @@ module Ticket_hash : sig
   end
 end
 
+(** This module re-exports definitions from {!Manager_counter_repr}. *)
+module Manager_counter : sig
+  include Compare.S
+
+  val succ : t -> t
+
+  val pp : Format.formatter -> t -> unit
+
+  val encoding_for_RPCs : t Data_encoding.t
+
+  module Internal_for_injection : sig
+    val of_string : string -> t option
+  end
+
+  module Internal_for_tests : sig
+    val of_int : int -> t
+
+    val to_int : t -> int
+
+    val add : t -> int -> t
+  end
+end
+
 (** This module re-exports definitions from {!Contract_repr} and
     {!Contract_storage}. *)
 module Contract : sig
@@ -1664,12 +1687,13 @@ module Contract : sig
     public_key ->
     context tzresult Lwt.t
 
-  val get_counter : context -> public_key_hash -> Z.t tzresult Lwt.t
+  val get_counter :
+    context -> public_key_hash -> Manager_counter.t tzresult Lwt.t
 
   val increment_counter : context -> public_key_hash -> context tzresult Lwt.t
 
   val check_counter_increment :
-    context -> public_key_hash -> Z.t -> unit tzresult Lwt.t
+    context -> public_key_hash -> Manager_counter.t -> unit tzresult Lwt.t
 
   (** See {!Contract_storage.check_allocated_and_get_balance}. *)
   val check_allocated_and_get_balance :
@@ -4346,7 +4370,7 @@ and _ contents =
   | Manager_operation : {
       source : public_key_hash;
       fee : Tez.tez;
-      counter : counter;
+      counter : Manager_counter.t;
       operation : 'kind manager_operation;
       gas_limit : Gas.Arith.integral;
       storage_limit : Z.t;
@@ -4503,8 +4527,6 @@ and _ manager_operation =
     }
       -> Kind.zk_rollup_publish manager_operation
 
-and counter = Z.t
-
 type packed_manager_operation =
   | Manager : 'kind manager_operation -> packed_manager_operation
 
diff --git a/src/proto_alpha/lib_protocol/contract_services.ml b/src/proto_alpha/lib_protocol/contract_services.ml
index b55fa2740e7b1370a78ee33588a5294864e1cb6a..0708612f1b4cef206c153c2ebb9c9eaa272ed928 100644
--- a/src/proto_alpha/lib_protocol/contract_services.ml
+++ b/src/proto_alpha/lib_protocol/contract_services.ml
@@ -37,7 +37,7 @@ let big_map_root =
 type info = {
   balance : Tez.t;
   delegate : public_key_hash option;
-  counter : counter option;
+  counter : Manager_counter.t option;
   script : Script.t option;
 }
 
@@ -52,7 +52,7 @@ let info_encoding =
        (req "balance" Tez.encoding)
        (opt "delegate" Signature.Public_key_hash.encoding)
        (opt "script" Script.encoding)
-       (opt "counter" n)
+       (opt "counter" Manager_counter.encoding_for_RPCs)
 
 let legacy = Script_ir_translator_config.make ~legacy:true ()
 
@@ -102,7 +102,7 @@ module S = struct
     RPC_service.get_service
       ~description:"Access the counter of a contract, if any."
       ~query:RPC_query.empty
-      ~output:z
+      ~output:Manager_counter.encoding_for_RPCs
       RPC_path.(custom_root /: Contract.rpc_arg / "counter")
 
   let script =
diff --git a/src/proto_alpha/lib_protocol/contract_services.mli b/src/proto_alpha/lib_protocol/contract_services.mli
index e37d2ce837f658572727122eedb3eb7b9a6a18db..7ea8996b24ab3b652a14a18a28c52a41d9901e0b 100644
--- a/src/proto_alpha/lib_protocol/contract_services.mli
+++ b/src/proto_alpha/lib_protocol/contract_services.mli
@@ -35,7 +35,7 @@ val list : 'a #RPC_context.simple -> 'a -> Contract.t list shell_tzresult Lwt.t
 type info = {
   balance : Tez.t;
   delegate : public_key_hash option;
-  counter : counter option;
+  counter : Manager_counter.t option;
   script : Script.t option;
 }
 
@@ -79,7 +79,7 @@ val counter :
   'a #RPC_context.simple ->
   'a ->
   public_key_hash ->
-  counter shell_tzresult Lwt.t
+  Manager_counter.t shell_tzresult Lwt.t
 
 val script :
   'a #RPC_context.simple ->
diff --git a/src/proto_alpha/lib_protocol/contract_storage.ml b/src/proto_alpha/lib_protocol/contract_storage.ml
index 1368f75f7aeb3607b88ef792570bc4ce69426729..ee95dfadaf3e38bc8a9e518e7e54d91d0c5a1b1b 100644
--- a/src/proto_alpha/lib_protocol/contract_storage.ml
+++ b/src/proto_alpha/lib_protocol/contract_storage.ml
@@ -30,14 +30,14 @@ type error +=
   | (* `Temporary *)
       Counter_in_the_past of {
       contract : Contract_repr.t;
-      expected : Z.t;
-      found : Z.t;
+      expected : Manager_counter_repr.t;
+      found : Manager_counter_repr.t;
     }
   | (* `Branch *)
       Counter_in_the_future of {
       contract : Contract_repr.t;
-      expected : Z.t;
-      found : Z.t;
+      expected : Manager_counter_repr.t;
+      found : Manager_counter_repr.t;
     }
   | (* `Temporary *)
       Non_existing_contract of Contract_repr.t
@@ -88,17 +88,17 @@ let () =
       Format.fprintf
         ppf
         "Counter %a not yet reached for contract %a (expected %a)"
-        Z.pp_print
+        Manager_counter_repr.pp
         found
         Contract_repr.pp
         contract
-        Z.pp_print
+        Manager_counter_repr.pp
         exp)
     Data_encoding.(
       obj3
         (req "contract" Contract_repr.encoding)
-        (req "expected" z)
-        (req "found" z))
+        (req "expected" Manager_counter_repr.encoding_for_errors)
+        (req "found" Manager_counter_repr.encoding_for_errors))
     (function
       | Counter_in_the_future {contract; expected; found} ->
           Some (contract, expected, found)
@@ -114,17 +114,17 @@ let () =
       Format.fprintf
         ppf
         "Counter %a already used for contract %a (expected %a)"
-        Z.pp_print
+        Manager_counter_repr.pp
         found
         Contract_repr.pp
         contract
-        Z.pp_print
+        Manager_counter_repr.pp
         exp)
     Data_encoding.(
       obj3
         (req "contract" Contract_repr.encoding)
-        (req "expected" z)
-        (req "found" z))
+        (req "expected" Manager_counter_repr.encoding_for_errors)
+        (req "found" Manager_counter_repr.encoding_for_errors))
     (function
       | Counter_in_the_past {contract; expected; found} ->
           Some (contract, expected, found)
@@ -504,18 +504,24 @@ let originated_from_current_nonce ~since:ctxt_since ~until:ctxt_until =
 let check_counter_increment c manager counter =
   let contract = Contract_repr.Implicit manager in
   Storage.Contract.Counter.get c contract >>=? fun contract_counter ->
-  let expected = Z.succ contract_counter in
-  if Compare.Z.(expected = counter) then return_unit
-  else if Compare.Z.(expected > counter) then
+  let expected = Manager_counter_repr.succ contract_counter in
+  if Manager_counter_repr.(expected = counter) then return_unit
+  else if Manager_counter_repr.(expected > counter) then
     fail (Counter_in_the_past {contract; expected; found = counter})
   else fail (Counter_in_the_future {contract; expected; found = counter})
 
 let increment_counter c manager =
   let contract = Contract_repr.Implicit manager in
   Storage.Contract.Global_counter.get c >>=? fun global_counter ->
-  Storage.Contract.Global_counter.update c (Z.succ global_counter) >>=? fun c ->
+  Storage.Contract.Global_counter.update
+    c
+    (Manager_counter_repr.succ global_counter)
+  >>=? fun c ->
   Storage.Contract.Counter.get c contract >>=? fun contract_counter ->
-  Storage.Contract.Counter.update c contract (Z.succ contract_counter)
+  Storage.Contract.Counter.update
+    c
+    contract
+    (Manager_counter_repr.succ contract_counter)
 
 let get_script_code c contract_hash =
   let contract = Contract_repr.Originated contract_hash in
@@ -634,7 +640,7 @@ let credit_only_call_from_token c contract amount =
       Stake_storage.add_contract_stake c contract amount
 
 let init c =
-  Storage.Contract.Global_counter.init c Z.zero >>=? fun c ->
+  Storage.Contract.Global_counter.init c Manager_counter_repr.init >>=? fun c ->
   Lazy_storage_diff.init c
 
 let used_storage_space c contract =
diff --git a/src/proto_alpha/lib_protocol/contract_storage.mli b/src/proto_alpha/lib_protocol/contract_storage.mli
index e553be0458957fa2294b742e63ffae16f6eba838..23c062aad53bf2e5fd68847c38ce4a3235a3c3da 100644
--- a/src/proto_alpha/lib_protocol/contract_storage.mli
+++ b/src/proto_alpha/lib_protocol/contract_storage.mli
@@ -32,14 +32,14 @@ type error +=
   | (* `Temporary *)
       Counter_in_the_past of {
       contract : Contract_repr.t;
-      expected : Z.t;
-      found : Z.t;
+      expected : Manager_counter_repr.t;
+      found : Manager_counter_repr.t;
     }
   | (* `Branch *)
       Counter_in_the_future of {
       contract : Contract_repr.t;
-      expected : Z.t;
-      found : Z.t;
+      expected : Manager_counter_repr.t;
+      found : Manager_counter_repr.t;
     }
   | (* `Temporary *)
       Non_existing_contract of Contract_repr.t
@@ -80,7 +80,10 @@ val must_be_allocated : Raw_context.t -> Contract_repr.t -> unit tzresult Lwt.t
 val list : Raw_context.t -> Contract_repr.t list Lwt.t
 
 val check_counter_increment :
-  Raw_context.t -> Signature.Public_key_hash.t -> Z.t -> unit tzresult Lwt.t
+  Raw_context.t ->
+  Signature.Public_key_hash.t ->
+  Manager_counter_repr.t ->
+  unit tzresult Lwt.t
 
 val increment_counter :
   Raw_context.t -> Signature.Public_key_hash.t -> Raw_context.t tzresult Lwt.t
@@ -107,7 +110,9 @@ val check_allocated_and_get_balance :
   Raw_context.t -> Signature.public_key_hash -> Tez_repr.t tzresult Lwt.t
 
 val get_counter :
-  Raw_context.t -> Signature.Public_key_hash.t -> Z.t tzresult Lwt.t
+  Raw_context.t ->
+  Signature.Public_key_hash.t ->
+  Manager_counter_repr.t tzresult Lwt.t
 
 val get_script_code :
   Raw_context.t ->
diff --git a/src/proto_alpha/lib_protocol/dune b/src/proto_alpha/lib_protocol/dune
index 65a9fe15d97539f3bfc335c7eba269ceb1ddc3fb..70b931f52b641519290273a132ad23232974a7b7 100644
--- a/src/proto_alpha/lib_protocol/dune
+++ b/src/proto_alpha/lib_protocol/dune
@@ -72,6 +72,7 @@
   Sampler
   Voting_period_repr
   Ticket_hash_repr
+  Manager_counter_repr
   Contract_repr
   Indexable
   Entrypoint_repr
@@ -339,6 +340,7 @@
   sampler.ml sampler.mli
   voting_period_repr.ml voting_period_repr.mli
   ticket_hash_repr.ml ticket_hash_repr.mli
+  manager_counter_repr.ml manager_counter_repr.mli
   contract_repr.ml contract_repr.mli
   indexable.ml indexable.mli
   entrypoint_repr.ml entrypoint_repr.mli
@@ -588,6 +590,7 @@
   sampler.ml sampler.mli
   voting_period_repr.ml voting_period_repr.mli
   ticket_hash_repr.ml ticket_hash_repr.mli
+  manager_counter_repr.ml manager_counter_repr.mli
   contract_repr.ml contract_repr.mli
   indexable.ml indexable.mli
   entrypoint_repr.ml entrypoint_repr.mli
@@ -842,6 +845,7 @@
   sampler.ml sampler.mli
   voting_period_repr.ml voting_period_repr.mli
   ticket_hash_repr.ml ticket_hash_repr.mli
+  manager_counter_repr.ml manager_counter_repr.mli
   contract_repr.ml contract_repr.mli
   indexable.ml indexable.mli
   entrypoint_repr.ml entrypoint_repr.mli
diff --git a/src/proto_alpha/lib_protocol/manager_counter_repr.ml b/src/proto_alpha/lib_protocol/manager_counter_repr.ml
new file mode 100644
index 0000000000000000000000000000000000000000..9e93014af743ab107c4490076a8559d4d54b44d1
--- /dev/null
+++ b/src/proto_alpha/lib_protocol/manager_counter_repr.ml
@@ -0,0 +1,61 @@
+(*****************************************************************************)
+(*                                                                           *)
+(* Open Source License                                                       *)
+(* Copyright (c) 2018 Dynamic Ledger Solutions, Inc. <contact@tezos.com>     *)
+(* Copyright (c) 2022 Nomadic Labs <contact@nomadic-labs.com>                *)
+(*                                                                           *)
+(* Permission is hereby granted, free of charge, to any person obtaining a   *)
+(* copy of this software and associated documentation files (the "Software"),*)
+(* to deal in the Software without restriction, including without limitation *)
+(* the rights to use, copy, modify, merge, publish, distribute, sublicense,  *)
+(* and/or sell copies of the Software, and to permit persons to whom the     *)
+(* Software is furnished to do so, subject to the following conditions:      *)
+(*                                                                           *)
+(* The above copyright notice and this permission notice shall be included   *)
+(* in all copies or substantial portions of the Software.                    *)
+(*                                                                           *)
+(* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR*)
+(* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,  *)
+(* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL   *)
+(* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER*)
+(* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING   *)
+(* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER       *)
+(* DEALINGS IN THE SOFTWARE.                                                 *)
+(*                                                                           *)
+(*****************************************************************************)
+
+include Compare.Z
+
+let init = Z.zero
+
+let succ = Z.succ
+
+let pp = Z.pp_print
+
+let encoding_for_storage = Data_encoding.z
+
+let encoding_for_operation = Data_encoding.(check_size 10 n)
+
+let encoding_for_RPCs = Data_encoding.n
+
+let encoding_for_errors = Data_encoding.z
+
+module Internal_for_injection = struct
+  let of_string s =
+    match Z.of_string s with
+    | exception _ -> None
+    | z -> if z < Z.zero then None else Some z
+end
+
+module Internal_for_tests = struct
+  let of_int i =
+    assert (Compare.Int.(i >= 0)) ;
+    Z.of_int i
+
+  let to_int = Z.to_int
+
+  let add c i =
+    let c = Z.(add c (of_int i)) in
+    assert (c >= Z.zero) ;
+    c
+end
diff --git a/src/proto_alpha/lib_protocol/manager_counter_repr.mli b/src/proto_alpha/lib_protocol/manager_counter_repr.mli
new file mode 100644
index 0000000000000000000000000000000000000000..50fdf8e1ded5dbba6bbb391b5bd44b4038c9a279
--- /dev/null
+++ b/src/proto_alpha/lib_protocol/manager_counter_repr.mli
@@ -0,0 +1,69 @@
+(*****************************************************************************)
+(*                                                                           *)
+(* Open Source License                                                       *)
+(* Copyright (c) 2018 Dynamic Ledger Solutions, Inc. <contact@tezos.com>     *)
+(* Copyright (c) 2022 Nomadic Labs <contact@nomadic-labs.com>                *)
+(*                                                                           *)
+(* Permission is hereby granted, free of charge, to any person obtaining a   *)
+(* copy of this software and associated documentation files (the "Software"),*)
+(* to deal in the Software without restriction, including without limitation *)
+(* the rights to use, copy, modify, merge, publish, distribute, sublicense,  *)
+(* and/or sell copies of the Software, and to permit persons to whom the     *)
+(* Software is furnished to do so, subject to the following conditions:      *)
+(*                                                                           *)
+(* The above copyright notice and this permission notice shall be included   *)
+(* in all copies or substantial portions of the Software.                    *)
+(*                                                                           *)
+(* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR*)
+(* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,  *)
+(* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL   *)
+(* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER*)
+(* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING   *)
+(* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER       *)
+(* DEALINGS IN THE SOFTWARE.                                                 *)
+(*                                                                           *)
+(*****************************************************************************)
+
+(** Counters are used as anti-replay protection mechanism in
+    manager operations: each manager account stores a counter and
+    each manager operation declares a value for the counter. When
+    a manager operation is applied, the value of the counter of
+    its manager is checked and incremented. *)
+
+include Compare.S
+
+(** Initial value for a counter (zero). *)
+val init : t
+
+(** Successor of a counter. *)
+val succ : t -> t
+
+(** Pretty-printer for counters. *)
+val pp : Format.formatter -> t -> unit
+
+(** Encoding for a counter to be used in {!Storage}. *)
+val encoding_for_storage : t Data_encoding.t
+
+(** Encoding for a counter to be used in {!Operation_repr}. *)
+val encoding_for_operation : t Data_encoding.t
+
+(** Encoding for a counter to be used in RPCs. *)
+val encoding_for_RPCs : t Data_encoding.t
+
+(** Encoding for a counter to be used in errors. *)
+val encoding_for_errors : t Data_encoding.t
+
+(** To be used in client injection only. *)
+module Internal_for_injection : sig
+  (** Converts a string to a counter.
+      Returns [None] if the string does not represent a valid counter. *)
+  val of_string : string -> t option
+end
+
+module Internal_for_tests : sig
+  val of_int : int -> t
+
+  val to_int : t -> int
+
+  val add : t -> int -> t
+end
diff --git a/src/proto_alpha/lib_protocol/operation_repr.ml b/src/proto_alpha/lib_protocol/operation_repr.ml
index 41ad4307c084dd1963a3082d587218939829b54f..44a02137c32c8a84568df22b341c486400b194e6 100644
--- a/src/proto_alpha/lib_protocol/operation_repr.ml
+++ b/src/proto_alpha/lib_protocol/operation_repr.ml
@@ -330,7 +330,7 @@ and _ contents =
   | Manager_operation : {
       source : Signature.public_key_hash;
       fee : Tez_repr.tez;
-      counter : counter;
+      counter : Manager_counter_repr.t;
       operation : 'kind manager_operation;
       gas_limit : Gas_limit_repr.Arith.integral;
       storage_limit : Z.t;
@@ -489,8 +489,6 @@ and _ manager_operation =
     }
       -> Kind.zk_rollup_publish manager_operation
 
-and counter = Z.t
-
 let manager_kind : type kind. kind manager_operation -> kind Kind.manager =
   function
   | Reveal _ -> Kind.Reveal_manager_kind
@@ -1607,7 +1605,7 @@ module Encoding = struct
     obj5
       (req "source" Signature.Public_key_hash.encoding)
       (req "fee" Tez_repr.encoding)
-      (req "counter" (check_size 10 n))
+      (req "counter" Manager_counter_repr.encoding_for_operation)
       (req "gas_limit" (check_size 10 Gas_limit_repr.Arith.n_integral_encoding))
       (req "storage_limit" (check_size 10 n))
 
diff --git a/src/proto_alpha/lib_protocol/operation_repr.mli b/src/proto_alpha/lib_protocol/operation_repr.mli
index 27cc6c17cfd7ff2c6c632e87658a3318bf39dfba..18573215474ba8682a8fa1a3e8fd546834d0ae09 100644
--- a/src/proto_alpha/lib_protocol/operation_repr.mli
+++ b/src/proto_alpha/lib_protocol/operation_repr.mli
@@ -354,7 +354,7 @@ and _ contents =
   | Manager_operation : {
       source : Signature.Public_key_hash.t;
       fee : Tez_repr.tez;
-      counter : counter;
+      counter : Manager_counter_repr.t;
       operation : 'kind manager_operation;
       gas_limit : Gas_limit_repr.Arith.integral;
       storage_limit : Z.t;
@@ -581,13 +581,6 @@ and _ manager_operation =
     }
       -> Kind.zk_rollup_publish manager_operation
 
-(** Counters are used as anti-replay protection mechanism in
-    manager operations: each manager account stores a counter and
-    each manager operation declares a value for the counter. When
-    a manager operation is applied, the value of the counter of
-    its manager is checked and incremented. *)
-and counter = Z.t
-
 type packed_manager_operation =
   | Manager : 'kind manager_operation -> packed_manager_operation
 
diff --git a/src/proto_alpha/lib_protocol/storage.ml b/src/proto_alpha/lib_protocol/storage.ml
index f75a7e0216f4a45944e316ff2bfb65ca1331f839..274acf2e0491674f1002a960311dea33b7a6db8b 100644
--- a/src/proto_alpha/lib_protocol/storage.ml
+++ b/src/proto_alpha/lib_protocol/storage.ml
@@ -51,6 +51,12 @@ module Encoding = struct
 
     let encoding = Data_encoding.z
   end
+
+  module Manager_counter : VALUE with type t = Manager_counter_repr.t = struct
+    type t = Manager_counter_repr.t
+
+    let encoding = Manager_counter_repr.encoding_for_storage
+  end
 end
 
 module Int31_index : INDEX with type t = int = struct
@@ -169,12 +175,13 @@ module Contract = struct
         let name = ["contracts"]
       end)
 
-  module Global_counter : Simple_single_data_storage with type value = Z.t =
+  module Global_counter :
+    Simple_single_data_storage with type value = Manager_counter_repr.t =
     Make_single_data_storage (Registered) (Raw_context)
       (struct
         let name = ["global_counter"]
       end)
-      (Encoding.Z)
+      (Encoding.Manager_counter)
 
   module Indexed_context =
     Make_indexed_subcontext
@@ -271,7 +278,7 @@ module Contract = struct
       (struct
         let name = ["counter"]
       end)
-      (Encoding.Z)
+      (Encoding.Manager_counter)
 
   (* Consume gas for serialization and deserialization of expr in this
      module *)
diff --git a/src/proto_alpha/lib_protocol/storage.mli b/src/proto_alpha/lib_protocol/storage.mli
index 3c545c6b4c66378835938f2e4b7c7bfbd314603b..7e6da9f6dd3d11f2ae3ad33d62e8b92bba58d789 100644
--- a/src/proto_alpha/lib_protocol/storage.mli
+++ b/src/proto_alpha/lib_protocol/storage.mli
@@ -57,7 +57,8 @@ module Contract : sig
   (** Storage from this submodule must only be accessed through the
       module `Contract`. *)
 
-  module Global_counter : Simple_single_data_storage with type value = Z.t
+  module Global_counter :
+    Simple_single_data_storage with type value = Manager_counter_repr.t
 
   (** The domain of alive contracts *)
   val fold :
@@ -176,7 +177,7 @@ module Contract : sig
   module Counter :
     Indexed_data_storage_with_local_context
       with type key = Contract_repr.t
-       and type value = Z.t
+       and type value = Manager_counter_repr.t
        and type t := Raw_context.t
        and type local_context := local_context
 
diff --git a/src/proto_alpha/lib_protocol/test/helpers/context.mli b/src/proto_alpha/lib_protocol/test/helpers/context.mli
index 6d6e1d44f703ea716b4315664506437a08c81bc5..22366748fc543ad72786f25f48d46e7d513e8089 100644
--- a/src/proto_alpha/lib_protocol/test/helpers/context.mli
+++ b/src/proto_alpha/lib_protocol/test/helpers/context.mli
@@ -161,7 +161,7 @@ module Contract : sig
 
   val balance_and_frozen_bonds : t -> Contract.t -> Tez.t tzresult Lwt.t
 
-  val counter : t -> Contract.t -> Z.t tzresult Lwt.t
+  val counter : t -> Contract.t -> Manager_counter.t tzresult Lwt.t
 
   val manager : t -> Contract.t -> Account.t tzresult Lwt.t
 
diff --git a/src/proto_alpha/lib_protocol/test/helpers/op.ml b/src/proto_alpha/lib_protocol/test/helpers/op.ml
index 134d1d8ba66ac4029e51571f95c63e045cfb01e6..77943cf8968029ce63926da8545841cd31367f59 100644
--- a/src/proto_alpha/lib_protocol/test/helpers/op.ml
+++ b/src/proto_alpha/lib_protocol/test/helpers/op.ml
@@ -139,10 +139,10 @@ let batch_operations ?(recompute_counters = false) ~source ctxt
      List.fold_left
        (fun (counter, acc) -> function
          | Contents (Manager_operation m) ->
-             ( Z.succ counter,
+             ( Manager_counter.succ counter,
                Contents (Manager_operation {m with counter}) :: acc )
          | x -> (counter, x :: acc))
-       (Z.succ counter, [])
+       (Manager_counter.succ counter, [])
        operations
    in
    return (List.rev rev_operations)
@@ -211,7 +211,7 @@ let combine_operations ?public_key ?counter ?spurious_operation ~source ctxt
   | None -> Context.Contract.counter ctxt source)
   >>=? fun counter ->
   (* We increment the counter *)
-  let counter = Z.succ counter in
+  let counter = Manager_counter.succ counter in
   Context.Contract.manager ctxt source >>=? fun account ->
   let public_key = Option.value ~default:account.pk public_key in
   (Context.Contract.is_manager_key_revealed ctxt source >|=? function
@@ -227,7 +227,7 @@ let combine_operations ?public_key ?counter ?spurious_operation ~source ctxt
              storage_limit = Z.zero;
            }
        in
-       (Some (Contents reveal_op), Z.succ counter)
+       (Some (Contents reveal_op), Manager_counter.succ counter)
    | true -> (None, counter))
   >>=? fun (manager_op, counter) ->
   (* Update counters and transform into a contents_list *)
@@ -235,7 +235,7 @@ let combine_operations ?public_key ?counter ?spurious_operation ~source ctxt
     List.fold_left
       (fun (counter, acc) -> function
         | Contents (Manager_operation m) ->
-            ( Z.succ counter,
+            ( Manager_counter.succ counter,
               Contents (Manager_operation {m with counter}) :: acc )
         | x -> (counter, x :: acc))
       (counter, match manager_op with None -> [] | Some op -> [op])
@@ -280,7 +280,7 @@ let manager_operation ?(force_reveal = false) ?counter ?(fee = Tez.zero)
   resolve_gas_limit ctxt gas_limit >>=? fun gas_limit ->
   Context.Contract.manager ctxt source >>=? fun account ->
   let public_key = Option.value ~default:account.pk public_key in
-  let counter = Z.succ counter in
+  let counter = Manager_counter.succ counter in
   Context.Contract.is_manager_key_revealed ctxt source >|=? fun revealed ->
   (* If the manager is revealed or we are not forcing reveals, we
      generate a singleton manager operation. *)
@@ -317,7 +317,7 @@ let manager_operation ?(force_reveal = false) ?counter ?(fee = Tez.zero)
         {
           source = Signature.Public_key.hash public_key;
           fee;
-          counter = Z.succ counter;
+          counter = Manager_counter.succ counter;
           operation;
           gas_limit;
           storage_limit;
@@ -343,7 +343,7 @@ let revelation ?(fee = Tez.zero) ?(gas_limit = High) ?(storage_limit = Z.zero)
   | Some ctr -> return ctr)
   >>=? fun counter ->
   Context.Contract.manager ctxt source >|=? fun account ->
-  let counter = Z.succ counter in
+  let counter = Manager_counter.succ counter in
   let sop =
     Contents_list
       (Single
diff --git a/src/proto_alpha/lib_protocol/test/helpers/op.mli b/src/proto_alpha/lib_protocol/test/helpers/op.mli
index ce21e0ee036ad61b492e96f311a8f46146a1f35e..4b9df5708427d82fd52cced1afa55e7477d5042e 100644
--- a/src/proto_alpha/lib_protocol/test/helpers/op.mli
+++ b/src/proto_alpha/lib_protocol/test/helpers/op.mli
@@ -96,7 +96,7 @@ val pp_gas_limit : Format.formatter -> gas_limit -> unit
 
 val transaction :
   ?force_reveal:bool ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   ?fee:Tez.tez ->
   ?gas_limit:gas_limit ->
   ?storage_limit:Z.t ->
@@ -122,7 +122,7 @@ val transaction :
     yet. Disabled (set to [false]) by default.}} *)
 val unsafe_transaction :
   ?force_reveal:bool ->
-  ?counter:counter ->
+  ?counter:Manager_counter.t ->
   ?fee:Tez.t ->
   ?gas_limit:gas_limit ->
   ?storage_limit:Z.t ->
@@ -139,7 +139,7 @@ val delegation :
   ?force_reveal:bool ->
   ?fee:Tez.tez ->
   ?gas_limit:gas_limit ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   ?storage_limit:Z.t ->
   Context.t ->
   Contract.t ->
@@ -151,7 +151,7 @@ val set_deposits_limit :
   ?fee:Tez.tez ->
   ?gas_limit:gas_limit ->
   ?storage_limit:Z.t ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   Context.t ->
   Contract.t ->
   Tez.tez option ->
@@ -159,7 +159,7 @@ val set_deposits_limit :
 
 val increase_paid_storage :
   ?force_reveal:bool ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   ?fee:Tez.tez ->
   ?gas_limit:gas_limit ->
   ?storage_limit:Z.t ->
@@ -191,7 +191,7 @@ val revelation :
   ?fee:Tez.t ->
   ?gas_limit:gas_limit ->
   ?storage_limit:Z.t ->
-  ?counter:counter ->
+  ?counter:Manager_counter.t ->
   ?forge_pkh:public_key_hash option ->
   Context.t ->
   public_key ->
@@ -214,7 +214,7 @@ val failing_noop :
     yet. Disabled (set to [false]) by default.}} *)
 val contract_origination :
   ?force_reveal:bool ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   ?delegate:public_key_hash ->
   script:Script.t ->
   ?public_key:public_key ->
@@ -228,7 +228,7 @@ val contract_origination :
 
 val contract_origination_hash :
   ?force_reveal:bool ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   ?delegate:public_key_hash ->
   script:Script.t ->
   ?public_key:public_key ->
@@ -244,7 +244,7 @@ val originated_contract : Operation.packed -> Contract.t
 
 val register_global_constant :
   ?force_reveal:bool ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   ?public_key:Signature.public_key ->
   ?fee:Tez.tez ->
   ?gas_limit:gas_limit ->
@@ -282,7 +282,7 @@ val activation :
 
 val combine_operations :
   ?public_key:public_key ->
-  ?counter:counter ->
+  ?counter:Manager_counter.t ->
   ?spurious_operation:packed_operation ->
   source:Contract.t ->
   Context.t ->
@@ -372,7 +372,7 @@ val dummy_script_cost : Tez.t
     hash. *)
 val tx_rollup_origination :
   ?force_reveal:bool ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   ?fee:Tez.tez ->
   ?gas_limit:gas_limit ->
   ?storage_limit:Z.t ->
@@ -391,7 +391,7 @@ val tx_rollup_origination :
     yet. Disabled (set to [false]) by default.}} *)
 val tx_rollup_submit_batch :
   ?force_reveal:bool ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   ?fee:Tez.tez ->
   ?burn_limit:Tez.tez ->
   ?gas_limit:gas_limit ->
@@ -412,7 +412,7 @@ val tx_rollup_submit_batch :
     yet. Disabled (set to [false]) by default.}} *)
 val tx_rollup_commit :
   ?force_reveal:bool ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   ?fee:Tez.tez ->
   ?gas_limit:gas_limit ->
   ?storage_limit:Z.t ->
@@ -432,7 +432,7 @@ val tx_rollup_commit :
     yet. Disabled (set to [false]) by default..}} *)
 val tx_rollup_return_bond :
   ?force_reveal:bool ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   ?fee:Tez.tez ->
   ?gas_limit:gas_limit ->
   ?storage_limit:Z.t ->
@@ -451,7 +451,7 @@ val tx_rollup_return_bond :
     yet. Disabled (set to [false]) by default.}} *)
 val tx_rollup_finalize :
   ?force_reveal:bool ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   ?fee:Tez.tez ->
   ?gas_limit:gas_limit ->
   ?storage_limit:Z.t ->
@@ -464,7 +464,7 @@ val tx_rollup_finalize :
     remove a commitment from the rollup context. *)
 val tx_rollup_remove_commitment :
   ?force_reveal:bool ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   ?fee:Tez.tez ->
   ?gas_limit:gas_limit ->
   ?storage_limit:Z.t ->
@@ -486,7 +486,7 @@ val tx_rollup_remove_commitment :
     yet. Disabled (set to [false]) by default.}} *)
 val tx_rollup_dispatch_tickets :
   ?force_reveal:bool ->
-  ?counter:counter ->
+  ?counter:Manager_counter.t ->
   ?fee:Tez.t ->
   ?gas_limit:gas_limit ->
   ?storage_limit:Z.t ->
@@ -526,7 +526,7 @@ val tx_rollup_dispatch_tickets :
     yet. Disabled (set to [false]) by default.}} *)
 val transfer_ticket :
   ?force_reveal:bool ->
-  ?counter:counter ->
+  ?counter:Manager_counter.t ->
   ?fee:Tez.t ->
   ?gas_limit:gas_limit ->
   ?storage_limit:Z.t ->
@@ -547,7 +547,7 @@ val transfer_ticket :
     protocol. *)
 val tx_rollup_raw_reject :
   ?force_reveal:bool ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   ?fee:Tez.tez ->
   ?gas_limit:gas_limit ->
   ?storage_limit:Z.t ->
@@ -575,7 +575,7 @@ val tx_rollup_raw_reject :
     yet. Disabled (set to [false]) by default.}} *)
 val tx_rollup_reject :
   ?force_reveal:bool ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   ?fee:Tez.tez ->
   ?gas_limit:gas_limit ->
   ?storage_limit:Z.t ->
@@ -605,7 +605,7 @@ val tx_rollup_reject :
     yet. Disabled (set to [false]) by default.}} *)
 val sc_rollup_origination :
   ?force_reveal:bool ->
-  ?counter:counter ->
+  ?counter:Manager_counter.t ->
   ?fee:Tez.t ->
   ?gas_limit:gas_limit ->
   ?storage_limit:Z.t ->
@@ -628,7 +628,7 @@ val sc_rollup_origination :
     yet. Disabled (set to [false]) by default.}} *)
 val sc_rollup_publish :
   ?force_reveal:bool ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   ?fee:Tez.tez ->
   ?gas_limit:gas_limit ->
   ?storage_limit:Z.t ->
@@ -648,7 +648,7 @@ val sc_rollup_publish :
     yet. Disabled (set to [false]) by default.}} *)
 val sc_rollup_cement :
   ?force_reveal:bool ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   ?fee:Tez.tez ->
   ?gas_limit:gas_limit ->
   ?storage_limit:Z.t ->
@@ -659,7 +659,7 @@ val sc_rollup_cement :
   Operation.packed tzresult Lwt.t
 
 val sc_rollup_execute_outbox_message :
-  ?counter:counter ->
+  ?counter:Manager_counter.t ->
   ?fee:Tez.t ->
   ?gas_limit:gas_limit ->
   ?storage_limit:Z.t ->
@@ -673,7 +673,7 @@ val sc_rollup_execute_outbox_message :
 
 (** [sc_rollup_recover_bond ctxt source sc_rollup] returns a commitment bond. *)
 val sc_rollup_recover_bond :
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   ?fee:Tez.tez ->
   ?gas_limit:gas_limit ->
   ?storage_limit:Z.t ->
@@ -685,7 +685,7 @@ val sc_rollup_recover_bond :
 
 val sc_rollup_add_messages :
   ?force_reveal:bool ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   ?fee:Tez.tez ->
   ?gas_limit:gas_limit ->
   ?storage_limit:Z.t ->
@@ -696,7 +696,7 @@ val sc_rollup_add_messages :
 
 val sc_rollup_refute :
   ?force_reveal:bool ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   ?fee:Tez.tez ->
   ?gas_limit:gas_limit ->
   ?storage_limit:Z.t ->
@@ -709,7 +709,7 @@ val sc_rollup_refute :
 
 val sc_rollup_timeout :
   ?force_reveal:bool ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   ?fee:Tez.tez ->
   ?gas_limit:gas_limit ->
   ?storage_limit:Z.t ->
@@ -721,7 +721,7 @@ val sc_rollup_timeout :
 
 val dal_publish_slot_header :
   ?force_reveal:bool ->
-  ?counter:counter ->
+  ?counter:Manager_counter.t ->
   ?fee:Tez.t ->
   ?gas_limit:gas_limit ->
   ?storage_limit:Z.t ->
@@ -734,7 +734,7 @@ val dal_publish_slot_header :
     ~init_state ~nb_ops] tries to originate a ZK Rollup. *)
 val zk_rollup_origination :
   ?force_reveal:bool ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   ?fee:Tez.t ->
   ?gas_limit:gas_limit ->
   ?storage_limit:Z.t ->
@@ -750,7 +750,7 @@ val zk_rollup_origination :
 
 val update_consensus_key :
   ?force_reveal:bool ->
-  ?counter:counter ->
+  ?counter:Manager_counter.t ->
   ?fee:Tez.t ->
   ?gas_limit:gas_limit ->
   ?storage_limit:Z.t ->
@@ -770,7 +770,7 @@ val drain_delegate :
     to the pending list of a ZK Rollup. *)
 val zk_rollup_publish :
   ?force_reveal:bool ->
-  ?counter:Z.t ->
+  ?counter:Manager_counter.t ->
   ?fee:Tez.t ->
   ?gas_limit:gas_limit ->
   ?storage_limit:Z.t ->
diff --git a/src/proto_alpha/lib_protocol/test/helpers/operation_generator.ml b/src/proto_alpha/lib_protocol/test/helpers/operation_generator.ml
index 55f556658c09424c127a79359993b80620659f06..d15e2e74dfc39a381f4d959f97cb3e53bff60e15 100644
--- a/src/proto_alpha/lib_protocol/test/helpers/operation_generator.ml
+++ b/src/proto_alpha/lib_protocol/test/helpers/operation_generator.ml
@@ -327,7 +327,7 @@ let random_contract_hash = QCheck2.Gen.oneofl contract_hashes
 let gen_counters =
   let open QCheck2.Gen in
   let+ i = nat in
-  Z.of_int i
+  Manager_counter.Internal_for_tests.of_int i
 
 let gen_ticket_amounts =
   let open QCheck2.Gen in
diff --git a/src/proto_alpha/lib_protocol/test/integration/michelson/test_typechecking.ml b/src/proto_alpha/lib_protocol/test/integration/michelson/test_typechecking.ml
index 8caf7bf01e6aee66dfeea834b17a88c84019580f..f813f58e7085c8276aafd35b2c62f3af328db65a 100644
--- a/src/proto_alpha/lib_protocol/test/integration/michelson/test_typechecking.ml
+++ b/src/proto_alpha/lib_protocol/test/integration/michelson/test_typechecking.ml
@@ -52,7 +52,7 @@ let sc_originate block contract parameters_ty =
   let kind = Sc_rollup.Kind.Example_arith in
   let* operation, rollup =
     Op.sc_rollup_origination
-      ~counter:(Z.of_int 0)
+      ~counter:(Manager_counter.Internal_for_tests.of_int 0)
       (B block)
       contract
       kind
diff --git a/src/proto_alpha/lib_protocol/test/integration/operations/test_combined_operations.ml b/src/proto_alpha/lib_protocol/test/integration/operations/test_combined_operations.ml
index 376ce44906d2a6cc0760dc4e5b36cd7264d3ec3d..8fc28644d5da08b44feda6dd38b4ceb073a4dcd7 100644
--- a/src/proto_alpha/lib_protocol/test/integration/operations/test_combined_operations.ml
+++ b/src/proto_alpha/lib_protocol/test/integration/operations/test_combined_operations.ml
@@ -92,7 +92,7 @@ let test_multiple_origination_and_delegation () =
       Op.contract_origination
         ~gas_limit
         ~delegate:delegate_pkh
-        ~counter:(Z.of_int i)
+        ~counter:(Manager_counter.Internal_for_tests.of_int i)
         ~fee:Tez.zero
         ~script:Op.dummy_script
         ~credit:(Test_tez.of_int 10)
@@ -327,7 +327,14 @@ let test_inconsistent_counters () =
   (* Make legit transfers, performing reveals *)
   Block.bake ~operations:[op1; op2] blk >>=? fun b ->
   (* Now, counter c1 = counter c2 = 1, Op.transaction builds with counter + 1 *)
-  Op.transaction ~gas_limit ~fee:Tez.one (B b) c1 c2 ~counter:Z.one Tez.one
+  Op.transaction
+    ~gas_limit
+    ~fee:Tez.one
+    (B b)
+    c1
+    c2
+    ~counter:(Manager_counter.Internal_for_tests.of_int 1)
+    Tez.one
   >>=? fun op1 ->
   Op.transaction
     ~gas_limit
@@ -335,7 +342,7 @@ let test_inconsistent_counters () =
     (B b)
     c1
     c2
-    ~counter:(Z.of_int 2)
+    ~counter:(Manager_counter.Internal_for_tests.of_int 2)
     Tez.one
   >>=? fun op2 ->
   Op.transaction
@@ -344,7 +351,7 @@ let test_inconsistent_counters () =
     (B b)
     c1
     c2
-    ~counter:(Z.of_int 2)
+    ~counter:(Manager_counter.Internal_for_tests.of_int 2)
     (Tez.of_mutez_exn 5_000L)
   >>=? fun op2' ->
   Op.transaction
@@ -353,7 +360,7 @@ let test_inconsistent_counters () =
     (B b)
     c1
     c2
-    ~counter:(Z.of_int 3)
+    ~counter:(Manager_counter.Internal_for_tests.of_int 3)
     Tez.one
   >>=? fun op3 ->
   Op.transaction
@@ -362,7 +369,7 @@ let test_inconsistent_counters () =
     (B b)
     c1
     c2
-    ~counter:(Z.of_int 4)
+    ~counter:(Manager_counter.Internal_for_tests.of_int 4)
     Tez.one
   >>=? fun op4 ->
   (* Canari: Check counters are ok *)
diff --git a/src/proto_alpha/lib_protocol/test/integration/operations/test_origination.ml b/src/proto_alpha/lib_protocol/test/integration/operations/test_origination.ml
index b0c1e8d97f9c905422543491f0ca688e712bfa7e..bb5d8af9c57ff860997aa905654ed5ebb0288348 100644
--- a/src/proto_alpha/lib_protocol/test/integration/operations/test_origination.ml
+++ b/src/proto_alpha/lib_protocol/test/integration/operations/test_origination.ml
@@ -236,7 +236,7 @@ let test_unparsable_script () =
             {
               source = pkh;
               fee = Tez.one;
-              counter = Z.of_int 1;
+              counter = Manager_counter.Internal_for_tests.of_int 1;
               operation = origination;
               gas_limit;
               storage_limit = Z.zero;
diff --git a/src/proto_alpha/lib_protocol/test/integration/operations/test_transfer.ml b/src/proto_alpha/lib_protocol/test/integration/operations/test_transfer.ml
index 6331befc44d7e344136e1d0a6b86261d9137052e..c1ab45367f30c142cc3809a74f2290ba0ca3c2a2 100644
--- a/src/proto_alpha/lib_protocol/test/integration/operations/test_transfer.ml
+++ b/src/proto_alpha/lib_protocol/test/integration/operations/test_transfer.ml
@@ -536,7 +536,7 @@ let invalid_counter_in_the_future () =
   Context.init2 () >>=? fun (b, (contract_1, contract_2)) ->
   Incremental.begin_construction b >>=? fun b ->
   Context.Contract.counter (I b) contract_1 >>=? fun cpt ->
-  let counter = Z.add cpt (Z.of_int 10) in
+  let counter = Manager_counter.Internal_for_tests.add cpt 10 in
   Op.transaction (I b) contract_1 contract_2 Tez.one ~counter >>=? fun op ->
   Incremental.add_operation b op >>= fun b ->
   Assert.proto_error ~loc:__LOC__ b (function
diff --git a/src/proto_alpha/lib_protocol/test/integration/operations/test_tx_rollup.ml b/src/proto_alpha/lib_protocol/test/integration/operations/test_tx_rollup.ml
index fb6d287d19742a3936bd93d370766e1c141b864c..aa59f2a42e715a82fd31557df251cebcf2d7d644 100644
--- a/src/proto_alpha/lib_protocol/test/integration/operations/test_tx_rollup.ml
+++ b/src/proto_alpha/lib_protocol/test/integration/operations/test_tx_rollup.ml
@@ -387,7 +387,7 @@ let make_deposit b tx_rollup l1_src addr =
   let parameters = print_deposit_arg (`Typed tx_rollup) (`Hash addr) in
   let fee = Test_tez.of_int 10 in
   Op.transaction
-    ~counter:(Z.of_int 2)
+    ~counter:(Manager_counter.Internal_for_tests.of_int 2)
     ~fee
     (B b)
     l1_src
@@ -874,7 +874,7 @@ let test_add_two_batches () =
   Context.Contract.counter (B b) contract >>=? fun counter ->
   let contents2 = "batch2" in
   Op.tx_rollup_submit_batch
-    ~counter:Z.(add counter (of_int 1))
+    ~counter:Manager_counter.(succ counter)
     (B b)
     contract
     tx_rollup
@@ -954,7 +954,10 @@ let fill_inbox b tx_rollup contract contents k =
     >>=? fun operation ->
     let new_inbox_size = inbox_size + message_size in
     if new_inbox_size < tx_rollup_inbox_limit then
-      fill_inbox new_inbox_size (Z.succ counter) (operation :: operations)
+      fill_inbox
+        new_inbox_size
+        (Manager_counter.succ counter)
+        (operation :: operations)
     else
       Incremental.begin_construction b >>=? fun i ->
       k i inbox_size (operation, operations)
@@ -1023,7 +1026,7 @@ let test_inbox_count_too_big () =
           (B b)
           [batch; op])
     >>=? fun op ->
-    if n > 0 then fill_inbox b (Z.succ counter) (n - 1) (Some op)
+    if n > 0 then fill_inbox b (Manager_counter.succ counter) (n - 1) (Some op)
     else return (op, counter)
   in
   Context.Contract.counter (B b) contract >>=? fun counter ->
@@ -1125,7 +1128,7 @@ let test_additional_space_allocation_for_valid_deposit () =
   let parameters = print_deposit_arg (`Typed tx_rollup) (`Hash pkh) in
   let fee = Test_tez.of_int 10 in
   Op.transaction
-    ~counter:(Z.of_int 2)
+    ~counter:(Manager_counter.Internal_for_tests.of_int 2)
     ~fee
     (B b)
     account
@@ -1268,7 +1271,7 @@ let test_invalid_deposit_too_big_ticket () =
   in
   let fee = Test_tez.of_int 10 in
   Op.transaction
-    ~counter:(Z.of_int 2)
+    ~counter:(Manager_counter.Internal_for_tests.of_int 2)
     ~fee
     (B b)
     account
@@ -1319,7 +1322,7 @@ let test_invalid_deposit_too_big_ticket_type () =
   in
   let fee = Test_tez.of_int 10 in
   Op.transaction
-    ~counter:(Z.of_int 2)
+    ~counter:(Manager_counter.Internal_for_tests.of_int 2)
     ~fee
     (B b)
     account
@@ -1376,7 +1379,7 @@ let test_valid_deposit_big_ticket () =
   in
   let fee = Test_tez.of_int 10 in
   Op.transaction
-    ~counter:(Z.of_int 2)
+    ~counter:(Manager_counter.Internal_for_tests.of_int 2)
     ~fee
     (B b)
     account
diff --git a/src/proto_alpha/lib_protocol/test/integration/validate/generator_descriptors.ml b/src/proto_alpha/lib_protocol/test/integration/validate/generator_descriptors.ml
index 712a0a7554fc7cc86755fe4b5abce55c9ae221fc..14c622a5fd6e70d8cd67f7a7da186b96ff792bf5 100644
--- a/src/proto_alpha/lib_protocol/test/integration/validate/generator_descriptors.ml
+++ b/src/proto_alpha/lib_protocol/test/integration/validate/generator_descriptors.ml
@@ -705,7 +705,8 @@ let manager_prelude (infos : Manager.infos) b =
   let add bootstrap counter ops ops_by_bootstrap =
     List.map
       (fun (bootstrap', counter', ops') ->
-        if bootstrap' = bootstrap then (bootstrap, Z.succ counter, ops)
+        if bootstrap' = bootstrap then
+          (bootstrap, Manager_counter.succ counter, ops)
         else (bootstrap', counter', ops'))
       ops_by_bootstrap
   in
diff --git a/src/proto_alpha/lib_protocol/test/integration/validate/generators.ml b/src/proto_alpha/lib_protocol/test/integration/validate/generators.ml
index 9db10ff3124b2c1d49cfe0ff7b02459be39ebcea..30967c0027ffb6ca5d934c05f32fd6d2a07575d3 100644
--- a/src/proto_alpha/lib_protocol/test/integration/validate/generators.ml
+++ b/src/proto_alpha/lib_protocol/test/integration/validate/generators.ml
@@ -136,13 +136,20 @@ let gen_pos : cstrs -> int option QCheck2.Gen.t =
       let+ v = int_range ~origin min max in
       Some v
 
-(** Generator for Z.t that is used for counter and gas limit. *)
+(** Generator for Z.t that is used for gas limit. *)
 let gen_z : cstrs -> Z.t option QCheck2.Gen.t =
  fun cstrs ->
   let open QCheck2.Gen in
   let+ v = gen_pos cstrs in
   Option.map Z.of_int v
 
+(** Generator for Manager_counter.t. *)
+let gen_counter : cstrs -> Manager_counter.t option QCheck2.Gen.t =
+ fun cstrs ->
+  let open QCheck2.Gen in
+  let+ v = gen_pos cstrs in
+  Option.map Manager_counter.Internal_for_tests.of_int v
+
 (** Generator for Tez.t. *)
 let gen_tez : cstrs -> Tez.t option QCheck2.Gen.t =
  fun cstrs ->
@@ -194,7 +201,7 @@ let gen_operation_req :
  fun {counter; fee; gas_limit; storage_limit; force_reveal; amount} subjects ->
   let open QCheck2.Gen in
   let* kind = gen_kind subjects in
-  let* counter = gen_z counter in
+  let* counter = gen_counter counter in
   let* fee = gen_tez fee in
   let* gas_limit = gen_gas_limit gas_limit in
   let* storage_limit = gen_z storage_limit in
@@ -212,7 +219,11 @@ let gen_2_operation_req :
   let* op1 =
     gen_operation_req {op_cstrs with force_reveal = Some true} subjects
   in
-  let counter = match op1.counter with Some x -> Z.to_int x | None -> 1 in
+  let counter =
+    match op1.counter with
+    | Some x -> Manager_counter.Internal_for_tests.to_int x
+    | None -> 1
+  in
   let op_cstr =
     {
       {op_cstrs with counter = Pure (counter + 2)} with
diff --git a/src/proto_alpha/lib_protocol/test/integration/validate/manager_operation_helpers.ml b/src/proto_alpha/lib_protocol/test/integration/validate/manager_operation_helpers.ml
index 8bacf024020b697c631d70c79cbf3e2cfab0a51e..4bb617d0b1f5b4624f996d2ade99889e2c5e6595 100644
--- a/src/proto_alpha/lib_protocol/test/integration/validate/manager_operation_helpers.ml
+++ b/src/proto_alpha/lib_protocol/test/integration/validate/manager_operation_helpers.ml
@@ -108,7 +108,7 @@ type manager_operation_kind =
 (** The requirements for a tested manager operation. *)
 type operation_req = {
   kind : manager_operation_kind;
-  counter : counter option;
+  counter : Manager_counter.t option;
   fee : Tez.t option;
   gas_limit : Op.gas_limit option;
   storage_limit : Z.t option;
@@ -226,7 +226,7 @@ let pp_operation_req pp
      amount: %a@,\
      @]"
     (kind_to_string kind)
-    (pp_opt Z.pp_print)
+    (pp_opt Manager_counter.pp)
     counter
     (pp_opt Tez.pp)
     fee
@@ -421,12 +421,12 @@ let fund_account_op block bootstrap account fund counter =
       (Contract.Implicit account)
       fund
   in
-  (op, Z.succ counter)
+  (op, Manager_counter.succ counter)
 
 let fund_account block bootstrap account fund =
   let open Lwt_result_syntax in
   let* counter = Context.Contract.counter (B block) bootstrap in
-  let* operation, (_counter : counter) =
+  let* operation, (_counter : Manager_counter.t) =
     fund_account_op block bootstrap account fund counter
   in
   let*! b = Block.bake ~operation block in
@@ -1322,7 +1322,9 @@ let expected_witness witness probes ~mode ctxt =
   let open Lwt_result_syntax in
   let b_in, c_in, g_in = witness in
   let*? b_expected = b_in -? probes.fee in
-  let c_expected = Z.add c_in (Z.of_int probes.nb_counter) in
+  let c_expected =
+    Manager_counter.Internal_for_tests.add c_in probes.nb_counter
+  in
   let+ g_expected =
     match (g_in, mode) with
     | Some g_in, Construction ->
@@ -1385,10 +1387,10 @@ let observe ~only_validate ~mode ctxt_pre ctxt_post op =
   let* () = b_cmp b_out b_expected in
   let _ =
     Assert.equal
-      Z.equal
+      Manager_counter.equal
       ~loc:__LOC__
       "Counter incrementation"
-      Z.pp_print
+      Manager_counter.pp
       c_out
       c_expected
   in
diff --git a/src/proto_alpha/lib_protocol/test/integration/validate/test_manager_operation_validation.ml b/src/proto_alpha/lib_protocol/test/integration/validate/test_manager_operation_validation.ml
index d5e81108f4266c0124aad7ff958ac9c2f9fbe038..e0ab92846cc9716979b7a02b006c15be10aa001e 100644
--- a/src/proto_alpha/lib_protocol/test/integration/validate/test_manager_operation_validation.ml
+++ b/src/proto_alpha/lib_protocol/test/integration/validate/test_manager_operation_validation.ml
@@ -164,7 +164,7 @@ let test_high_counter infos kind =
       {
         (operation_req_default kind) with
         force_reveal = Some true;
-        counter = Some (Z.of_int max_int);
+        counter = Some (Manager_counter.Internal_for_tests.of_int max_int);
       }
       infos
   in
@@ -202,7 +202,8 @@ let test_low_counter infos kind =
       {
         (operation_req_default kind) with
         force_reveal = Some true;
-        counter = Some (Z.sub current_counter Z.one);
+        counter =
+          Some (Manager_counter.Internal_for_tests.add current_counter (-1));
       }
       infos
   in
diff --git a/src/proto_alpha/lib_protocol/test/integration/validate/test_validation_batch.ml b/src/proto_alpha/lib_protocol/test/integration/validate/test_validation_batch.ml
index beff404e811fc454f8d59e9d81107089a4128f9f..ba364f0dc2f406015e5008bfd7e87b63ace740e8 100644
--- a/src/proto_alpha/lib_protocol/test/integration/validate/test_validation_batch.ml
+++ b/src/proto_alpha/lib_protocol/test/integration/validate/test_validation_batch.ml
@@ -63,7 +63,7 @@ let batch_in_the_middle infos kind1 kind2 =
       (B infos.ctxt.block)
       (contract_of (get_source infos))
   in
-  let counter = Z.succ counter in
+  let counter = Manager_counter.succ counter in
   let* operation1 =
     select_op
       {
@@ -73,7 +73,7 @@ let batch_in_the_middle infos kind1 kind2 =
       }
       infos
   in
-  let counter = Z.succ counter in
+  let counter = Manager_counter.succ counter in
   let* reveal =
     mk_reveal
       {
@@ -83,7 +83,7 @@ let batch_in_the_middle infos kind1 kind2 =
       }
       infos
   in
-  let counter = Z.succ counter in
+  let counter = Manager_counter.succ counter in
   let* operation2 =
     select_op
       {
@@ -126,7 +126,7 @@ let batch_two_reveals infos kind =
       (B infos.ctxt.block)
       (contract_of (get_source infos))
   in
-  let counter = Z.succ counter in
+  let counter = Manager_counter.succ counter in
   let* reveal =
     mk_reveal
       {
@@ -136,7 +136,7 @@ let batch_two_reveals infos kind =
       }
       infos
   in
-  let counter = Z.succ counter in
+  let counter = Manager_counter.succ counter in
   let* reveal1 =
     mk_reveal
       {
@@ -146,7 +146,7 @@ let batch_two_reveals infos kind =
       }
       infos
   in
-  let counter = Z.succ counter in
+  let counter = Manager_counter.succ counter in
   let* operation =
     select_op
       {
@@ -184,7 +184,7 @@ let batch_two_sources infos kind1 kind2 =
   let open Lwt_result_syntax in
   let source = contract_of (get_source infos) in
   let* counter = Context.Contract.counter (B infos.ctxt.block) source in
-  let counter = Z.succ counter in
+  let counter = Manager_counter.succ counter in
   let* operation1 =
     select_op
       {
@@ -225,9 +225,9 @@ let batch_incons_counters infos kind1 kind2 =
   let op_infos = {{op_infos with fee} with counter = Some counter} in
   let* reveal = mk_reveal op_infos infos in
   let counter0 = counter in
-  let counter = Z.succ counter in
-  let counter2 = Z.succ counter in
-  let counter3 = Z.succ counter2 in
+  let counter = Manager_counter.succ counter in
+  let counter2 = Manager_counter.succ counter in
+  let counter3 = Manager_counter.succ counter2 in
   let operation counter kind =
     select_op
       {
@@ -328,7 +328,7 @@ let batch_emptying_balance_in_the_middle infos kind1 kind2 =
       {(operation_req_default K_Reveal) with counter = Some counter}
       infos
   in
-  let counter = Z.succ counter in
+  let counter = Manager_counter.succ counter in
   let operation fee =
     select_op
       {
@@ -339,7 +339,7 @@ let batch_emptying_balance_in_the_middle infos kind1 kind2 =
       }
       infos
   in
-  let counter = Z.succ counter in
+  let counter = Manager_counter.succ counter in
   let operation2 fee =
     select_op
       {
@@ -389,7 +389,7 @@ let batch_empty_at_end infos kind1 kind2 =
       {(operation_req_default K_Reveal) with counter = Some counter}
       infos
   in
-  let counter = Z.succ counter in
+  let counter = Manager_counter.succ counter in
   let operation fee =
     select_op
       {
@@ -400,7 +400,7 @@ let batch_empty_at_end infos kind1 kind2 =
       }
       infos
   in
-  let counter = Z.succ counter in
+  let counter = Manager_counter.succ counter in
   let operation2 fee =
     select_op
       {
@@ -449,7 +449,7 @@ let batch_reveal_transaction infos =
       }
       infos
   in
-  let counter = Z.succ counter in
+  let counter = Manager_counter.succ counter in
   let* transaction =
     mk_transaction
       {
@@ -484,7 +484,7 @@ let batch_exceeding_block_gas ~mempool_mode infos kind1 kind2 =
       {(operation_req_default K_Reveal) with counter = Some counter}
       infos
   in
-  let counter = Z.succ counter in
+  let counter = Manager_counter.succ counter in
   let operation gas_limit =
     select_op
       {
@@ -495,7 +495,7 @@ let batch_exceeding_block_gas ~mempool_mode infos kind1 kind2 =
       }
       infos
   in
-  let counter = Z.succ counter in
+  let counter = Manager_counter.succ counter in
   let operation2 gas_limit =
     select_op
       {
diff --git a/src/proto_alpha/lib_protocol/validate.ml b/src/proto_alpha/lib_protocol/validate.ml
index 83414ab00446f2e0b37bcf6e15d09af57b7b3f92..bf3b54d7aa631318e16f51fb019f499771d7c9e3 100644
--- a/src/proto_alpha/lib_protocol/validate.ml
+++ b/src/proto_alpha/lib_protocol/validate.ml
@@ -2129,13 +2129,13 @@ module Manager = struct
           Inconsistent_sources
       in
       error_unless
-        Compare.Z.(Z.succ previous_counter = counter)
+        Manager_counter.(succ previous_counter = counter)
         Inconsistent_counters
     in
     let rec check_batch_tail_sanity :
         type kind.
         public_key_hash ->
-        counter ->
+        Manager_counter.t ->
         kind Kind.manager contents_list ->
         unit tzresult =
      fun expected_source previous_counter -> function
@@ -2163,7 +2163,7 @@ module Manager = struct
     let check_batch :
         type kind.
         kind Kind.manager contents_list ->
-        (public_key_hash * public_key option * counter) tzresult =
+        (public_key_hash * public_key option * Manager_counter.t) tzresult =
      fun contents_list ->
       match contents_list with
       | Single (Manager_operation {source; operation = Reveal key; counter; _})
diff --git a/src/proto_alpha/lib_tx_rollup/injector.ml b/src/proto_alpha/lib_tx_rollup/injector.ml
index 9d54d22f9e6ac7e478a520d76ef3fa5ac5564c58..108583dcae88e31dfe2596079b70cea930120c8d 100644
--- a/src/proto_alpha/lib_tx_rollup/injector.ml
+++ b/src/proto_alpha/lib_tx_rollup/injector.ml
@@ -125,7 +125,7 @@ module Parameters = struct
   let approximate_fee_bound _ _ =
     {
       fee = Tez.of_mutez_exn 3_000_000L;
-      counter = Z.of_int 500_000;
+      counter = Manager_counter.Internal_for_tests.of_int 500_000;
       gas_limit = Gas.Arith.integral_of_int_exn 500_000;
       storage_limit = Z.of_int 500_000;
     }