diff --git a/src/proto_alpha/lib_protocol/apply_results.ml b/src/proto_alpha/lib_protocol/apply_results.ml
index 346b542c012daef2ef0c84fa9df10ef34b11f9a4..5ca742c480b5c45f9a4a6c4da876787b7144f5f5 100644
--- a/src/proto_alpha/lib_protocol/apply_results.ml
+++ b/src/proto_alpha/lib_protocol/apply_results.ml
@@ -526,20 +526,15 @@ module Manager_result = struct
       ~op_case:Operation.Encoding.Manager_operations.update_consensus_key_case
       ~encoding:
         Data_encoding.(
-          obj2
-            (dft "consumed_gas" Gas.Arith.n_integral_encoding Gas.Arith.zero)
-            (dft "consumed_milligas" Gas.Arith.n_fp_encoding Gas.Arith.zero))
+          obj1 (dft "consumed_milligas" Gas.Arith.n_fp_encoding Gas.Arith.zero))
       ~select:(function
         | Successful_manager_result (Update_consensus_key_result _ as op) ->
             Some op
         | _ -> None)
       ~kind:Kind.Update_consensus_key_manager_kind
       ~proj:(function
-        | Update_consensus_key_result {consumed_gas} ->
-            (Gas.Arith.ceil consumed_gas, consumed_gas))
-      ~inj:(fun (consumed_gas, consumed_milligas) ->
-        assert (Gas.Arith.(equal (ceil consumed_milligas) consumed_gas)) ;
-        Update_consensus_key_result {consumed_gas = consumed_milligas})
+        | Update_consensus_key_result {consumed_gas} -> consumed_gas)
+      ~inj:(fun consumed_gas -> Update_consensus_key_result {consumed_gas})
 
   let set_deposits_limit_case =
     make
diff --git a/src/proto_alpha/lib_protocol/bootstrap_storage.ml b/src/proto_alpha/lib_protocol/bootstrap_storage.ml
index 02f7a938c93e83f9a140270cc2c0513ea4f79217..7c3de02badec173dfa832a420e0b505dbc34f574 100644
--- a/src/proto_alpha/lib_protocol/bootstrap_storage.ml
+++ b/src/proto_alpha/lib_protocol/bootstrap_storage.ml
@@ -53,7 +53,7 @@ let init_account (ctxt, balance_updates)
     amount
   >>=? fun (ctxt, new_balance_updates) ->
   (match public_key with
-  | Some public_key ->
+  | Some public_key -> (
       Contract_manager_storage.reveal_manager_key
         ctxt
         public_key_hash
@@ -64,11 +64,10 @@ let init_account (ctxt, balance_updates)
         contract
         (Some (Option.value ~default:public_key_hash delegate_to))
       >>=? fun ctxt ->
-      (match consensus_key with
+      match consensus_key with
       | None -> return ctxt
       | Some consensus_key ->
           Delegate_consensus_key.init ctxt public_key_hash consensus_key)
-      >>=? fun ctxt -> return ctxt
   | None ->
       fail_when
         (Option.is_some delegate_to)
diff --git a/src/proto_alpha/lib_protocol/delegate_consensus_key.ml b/src/proto_alpha/lib_protocol/delegate_consensus_key.ml
index 023247a68263803a0758d32ef3fd03d9be6c8fdb..3a96b922d1818fc56ce27fc11cc1efd1ba15dc14 100644
--- a/src/proto_alpha/lib_protocol/delegate_consensus_key.ml
+++ b/src/proto_alpha/lib_protocol/delegate_consensus_key.ml
@@ -85,20 +85,27 @@ let pp ppf {delegate; consensus_pkh} =
       consensus_pkh ;
   Format.fprintf ppf "@]"
 
-let check_inactive ctxt pkh =
+(* Invariant:
+      No two delegates use the same active consensus key at a given time.
+
+   To ensure that, {!Storage.Consensus_keys} contains keys that will be active
+   at cycle `current + preserved_cycles + 1`.
+*)
+
+let check_unused ctxt pkh =
   let open Lwt_tzresult_syntax in
   let*! is_active = Storage.Consensus_keys.mem ctxt pkh in
   fail_when is_active Invalid_consensus_key_update_active
 
-let set_inactive = Storage.Consensus_keys.remove
+let set_unused = Storage.Consensus_keys.remove
 
-let set_active = Storage.Consensus_keys.add
+let set_used = Storage.Consensus_keys.add
 
 let init ctxt delegate pk =
   let open Lwt_tzresult_syntax in
   let pkh = Signature.Public_key.hash pk in
-  let* () = check_inactive ctxt pkh in
-  let*! ctxt = set_active ctxt pkh in
+  let* () = check_unused ctxt pkh in
+  let*! ctxt = set_used ctxt pkh in
   Storage.Contract.Consensus_key.init ctxt (Contract_repr.Implicit delegate) pk
 
 let active_pubkey ctxt delegate =
@@ -170,12 +177,12 @@ let register_update ctxt delegate pk =
       (Invalid_consensus_key_update_noop first_active_cycle)
   in
   let pkh = Signature.Public_key.hash pk in
-  let* () = check_inactive ctxt pkh in
-  let*! ctxt = set_active ctxt pkh in
+  let* () = check_unused ctxt pkh in
+  let*! ctxt = set_used ctxt pkh in
   let* {consensus_pkh = old_pkh; _} =
     active_pubkey_for_cycle ctxt delegate update_cycle
   in
-  let*! ctxt = set_inactive ctxt old_pkh in
+  let*! ctxt = set_unused ctxt old_pkh in
   let*! ctxt =
     Storage.Contract.Pending_consensus_keys.add
       (ctxt, Contract_repr.Implicit delegate)
diff --git a/src/proto_alpha/lib_protocol/delegate_storage.ml b/src/proto_alpha/lib_protocol/delegate_storage.ml
index 373f18be208bea5e7c9062796f7bf34daeac52ac..f0bf60d9cd128e206ecf867d0bdc75f74b8d8be2 100644
--- a/src/proto_alpha/lib_protocol/delegate_storage.ml
+++ b/src/proto_alpha/lib_protocol/delegate_storage.ml
@@ -250,8 +250,9 @@ let delegated_balance ctxt delegate =
 
 let drain ctxt ~delegate ~destination =
   let open Lwt_tzresult_syntax in
+  let destination_contract = Contract_repr.Implicit destination in
   let*! is_destination_allocated =
-    Contract_storage.allocated ctxt (Contract_repr.Implicit destination)
+    Contract_storage.allocated ctxt destination_contract
   in
   let delegate_contract = Contract_repr.Implicit delegate in
   let* ctxt, _, balance_updates1 =
@@ -265,13 +266,13 @@ let drain ctxt ~delegate ~destination =
   let* manager_balance = spendable_balance ctxt delegate in
   let*? one_percent = Tez_repr.(manager_balance /? 100L) in
   let fees = Tez_repr.(max one one_percent) in
-  let*? transfered = Tez_repr.(manager_balance -? fees) in
+  let*? transferred = Tez_repr.(manager_balance -? fees) in
   let* ctxt, balance_updates2 =
     Token.transfer
       ctxt
       (`Contract delegate_contract)
-      (`Contract (Contract_repr.Implicit destination))
-      transfered
+      (`Contract destination_contract)
+      transferred
   in
   return
     ( ctxt,