diff --git a/src/lib_injector/injector_operation.ml b/src/lib_injector/injector_operation.ml
index 99525259b40d91f08fc55b8040a430128c2e1e92..61a28c2ccc8336f3c9f87d75bcfeefd0d25ec7f9 100644
--- a/src/lib_injector/injector_operation.ml
+++ b/src/lib_injector/injector_operation.ml
@@ -51,13 +51,26 @@ module Make (O : PARAM_OPERATION) :
 
   type t = {hash : hash; operation : O.t; mutable errors : errors}
 
-  let hash_inner_operation op =
-    Hash.hash_bytes [Data_encoding.Binary.to_bytes_exn O.encoding op]
+  let hash_inner_operation nonce op =
+    Hash.hash_string
+      [
+        Option.fold ~none:"" ~some:Z.to_bits nonce;
+        Data_encoding.Binary.to_string_exn O.encoding op;
+      ]
+
+  let counter = ref Z.zero
 
   let no_errors = {count = 0; last_error = None}
 
   let make operation =
-    let hash = hash_inner_operation operation in
+    let nonce =
+      if O.unique operation then (
+        let c = !counter in
+        counter := Z.succ !counter ;
+        Some c)
+      else None
+    in
+    let hash = hash_inner_operation nonce operation in
     {hash; operation; errors = no_errors}
 
   let errors_encoding =
diff --git a/src/lib_injector/injector_sigs.ml b/src/lib_injector/injector_sigs.ml
index f36dd6d3ae29ea381c114fb3b80facef89f3f8da..a3caa29d14621f203a9c48f50ae501b67247fa0f 100644
--- a/src/lib_injector/injector_sigs.ml
+++ b/src/lib_injector/injector_sigs.ml
@@ -97,6 +97,11 @@ module type PARAM_OPERATION = sig
 
   (** Pretty-printing injector's operations *)
   val pp : Format.formatter -> t -> unit
+
+  (** If [unique op = true], then the injector's queue will only contain at most
+      one operation [op]. Otherwise, it will allow duplicate such operations to
+      appear in the queue. *)
+  val unique : t -> bool
 end
 
 (** Internal representation of injector operations. *)
diff --git a/src/proto_016_PtMumbai/lib_sc_rollup_layer2/l1_operation.ml b/src/proto_016_PtMumbai/lib_sc_rollup_layer2/l1_operation.ml
index 1b3e165b794ff98f676d154ef7162e9703531525..686d7927381163e753afcbafee3af4459633533b 100644
--- a/src/proto_016_PtMumbai/lib_sc_rollup_layer2/l1_operation.ml
+++ b/src/proto_016_PtMumbai/lib_sc_rollup_layer2/l1_operation.ml
@@ -176,3 +176,7 @@ let of_manager_operation : type kind. kind manager_operation -> t option =
       Some (Refute {rollup; opponent; refutation})
   | Sc_rollup_timeout {rollup; stakers} -> Some (Timeout {rollup; stakers})
   | _ -> None
+
+let unique = function
+  | Add_messages _ -> false
+  | Cement _ | Publish _ | Refute _ | Timeout _ -> true
diff --git a/src/proto_016_PtMumbai/lib_sc_rollup_layer2/l1_operation.mli b/src/proto_016_PtMumbai/lib_sc_rollup_layer2/l1_operation.mli
index d6bd71285e0f47e35d01ce3f0f11fcbbb32dbfcb..953cd6f7fb5ee45675058819e90596711672bc56 100644
--- a/src/proto_016_PtMumbai/lib_sc_rollup_layer2/l1_operation.mli
+++ b/src/proto_016_PtMumbai/lib_sc_rollup_layer2/l1_operation.mli
@@ -48,3 +48,6 @@ val of_manager_operation : 'a manager_operation -> t option
 
 (** Pretty printer (human readable) for L1 operations. *)
 val pp : Format.formatter -> t -> unit
+
+(** [false] if the injector will accept duplicate such operations. *)
+val unique : t -> bool
diff --git a/src/proto_017_PtNairob/lib_sc_rollup_layer2/l1_operation.ml b/src/proto_017_PtNairob/lib_sc_rollup_layer2/l1_operation.ml
index 1b3e165b794ff98f676d154ef7162e9703531525..686d7927381163e753afcbafee3af4459633533b 100644
--- a/src/proto_017_PtNairob/lib_sc_rollup_layer2/l1_operation.ml
+++ b/src/proto_017_PtNairob/lib_sc_rollup_layer2/l1_operation.ml
@@ -176,3 +176,7 @@ let of_manager_operation : type kind. kind manager_operation -> t option =
       Some (Refute {rollup; opponent; refutation})
   | Sc_rollup_timeout {rollup; stakers} -> Some (Timeout {rollup; stakers})
   | _ -> None
+
+let unique = function
+  | Add_messages _ -> false
+  | Cement _ | Publish _ | Refute _ | Timeout _ -> true
diff --git a/src/proto_017_PtNairob/lib_sc_rollup_layer2/l1_operation.mli b/src/proto_017_PtNairob/lib_sc_rollup_layer2/l1_operation.mli
index d6bd71285e0f47e35d01ce3f0f11fcbbb32dbfcb..953cd6f7fb5ee45675058819e90596711672bc56 100644
--- a/src/proto_017_PtNairob/lib_sc_rollup_layer2/l1_operation.mli
+++ b/src/proto_017_PtNairob/lib_sc_rollup_layer2/l1_operation.mli
@@ -48,3 +48,6 @@ val of_manager_operation : 'a manager_operation -> t option
 
 (** Pretty printer (human readable) for L1 operations. *)
 val pp : Format.formatter -> t -> unit
+
+(** [false] if the injector will accept duplicate such operations. *)
+val unique : t -> bool
diff --git a/src/proto_alpha/lib_sc_rollup_layer2/l1_operation.ml b/src/proto_alpha/lib_sc_rollup_layer2/l1_operation.ml
index 1b3e165b794ff98f676d154ef7162e9703531525..686d7927381163e753afcbafee3af4459633533b 100644
--- a/src/proto_alpha/lib_sc_rollup_layer2/l1_operation.ml
+++ b/src/proto_alpha/lib_sc_rollup_layer2/l1_operation.ml
@@ -176,3 +176,7 @@ let of_manager_operation : type kind. kind manager_operation -> t option =
       Some (Refute {rollup; opponent; refutation})
   | Sc_rollup_timeout {rollup; stakers} -> Some (Timeout {rollup; stakers})
   | _ -> None
+
+let unique = function
+  | Add_messages _ -> false
+  | Cement _ | Publish _ | Refute _ | Timeout _ -> true
diff --git a/src/proto_alpha/lib_sc_rollup_layer2/l1_operation.mli b/src/proto_alpha/lib_sc_rollup_layer2/l1_operation.mli
index d6bd71285e0f47e35d01ce3f0f11fcbbb32dbfcb..953cd6f7fb5ee45675058819e90596711672bc56 100644
--- a/src/proto_alpha/lib_sc_rollup_layer2/l1_operation.mli
+++ b/src/proto_alpha/lib_sc_rollup_layer2/l1_operation.mli
@@ -48,3 +48,6 @@ val of_manager_operation : 'a manager_operation -> t option
 
 (** Pretty printer (human readable) for L1 operations. *)
 val pp : Format.formatter -> t -> unit
+
+(** [false] if the injector will accept duplicate such operations. *)
+val unique : t -> bool
diff --git a/tezt/tests/sc_rollup.ml b/tezt/tests/sc_rollup.ml
index 5a862f4a71497edd8e392a799da4cedee7ae4f66..87ddd7a03d80f2ff41cf7686c66b8361cbf88172 100644
--- a/tezt/tests/sc_rollup.ml
+++ b/tezt/tests/sc_rollup.ml
@@ -1068,6 +1068,10 @@ let bake_until_lpc_updated ?hook ?(at_least = 0) ?(timeout = 15.) client
   let* _ = Sc_rollup_node.wait_sync sc_rollup_node ~timeout:3. in
   return updated_level
 
+let check_batcher_message_status response status =
+  Check.((JSON.(response |-> "status" |> as_string) = status) string)
+    ~error_msg:"Status of message is %L but expected %R."
+
 (* Rollup node batcher *)
 let sc_rollup_node_batcher sc_rollup_node sc_rollup_client sc_rollup node client
     =
@@ -1081,11 +1085,8 @@ let sc_rollup_node_batcher sc_rollup_node sc_rollup_client sc_rollup node client
   let*! retrieved_msg1, status_msg1 =
     Sc_rollup_client.get_batcher_msg sc_rollup_client msg1_hash
   in
-  let check_status response status =
-    Check.((JSON.(response |-> "status" |> as_string) = status) string)
-      ~error_msg:"Status of message  is %L but expected %R."
-  in
-  check_status status_msg1 "pending_batch" ;
+
+  check_batcher_message_status status_msg1 "pending_batch" ;
   Check.((retrieved_msg1 = msg1) string)
     ~error_msg:"Message in queue is %L but injected %R." ;
   let*! queue = Sc_rollup_client.batcher_queue sc_rollup_client in
@@ -1100,13 +1101,13 @@ let sc_rollup_node_batcher sc_rollup_node sc_rollup_client sc_rollup node client
   let*! _msg1, status_msg1 =
     Sc_rollup_client.get_batcher_msg sc_rollup_client msg1_hash
   in
-  check_status status_msg1 "injected" ;
+  check_batcher_message_status status_msg1 "injected" ;
   (* We bake so that msg1 is included. *)
   let* () = Client.bake_for_and_wait client in
   let*! _msg1, status_msg1 =
     Sc_rollup_client.get_batcher_msg sc_rollup_client msg1_hash
   in
-  check_status status_msg1 "included" ;
+  check_batcher_message_status status_msg1 "included" ;
   let* _ =
     Sc_rollup_node.wait_for_level
       ~timeout:3.
@@ -1184,7 +1185,7 @@ let sc_rollup_node_batcher sc_rollup_node sc_rollup_client sc_rollup node client
   let*! _msg1, status_msg1 =
     Sc_rollup_client.get_batcher_msg sc_rollup_client msg1_hash
   in
-  check_status status_msg1 "committed" ;
+  check_batcher_message_status status_msg1 "committed" ;
   unit
 
 (* One can retrieve the list of originated SCORUs.
@@ -5237,6 +5238,48 @@ let test_bootstrap_smart_rollup_originated =
       ~error_msg:"Expected %R bootstrapped smart rollups, got %L") ;
   unit
 
+let test_inject_identital_messages ~kind =
+  test_full_scenario
+    ~kind
+    {
+      tags = ["injector"; "inject"; "identical"];
+      variant = None;
+      description = "The injector can inject identical messages";
+    }
+  @@ fun _protocol sc_rollup_node sc_rollup_client sc_rollup _node client ->
+  let* () =
+    Sc_rollup_node.run ~event_level:`Debug sc_rollup_node sc_rollup []
+  in
+  let check_status response status =
+    Check.((JSON.(response |-> "status" |> as_string) = status) string)
+      ~error_msg:"Status of message is %L but expected %R."
+  in
+  (* Produce artificially what two large [Sc_rollup_add_messages] would look like.
+     As the batches are the same, if we don't allow identical operations
+     in the injector, only the first hashes will be included, as the two
+     manager operations are the same.
+  *)
+  let s = String.make 4090 'a' in
+  let msgs = List.init 7 (fun _ -> s) in
+  let*! hashes1 = Sc_rollup_client.inject sc_rollup_client msgs in
+  let*! hashes2 = Sc_rollup_client.inject sc_rollup_client msgs in
+  let hash1 = Stdlib.List.hd hashes1 in
+  let hash2 = Stdlib.List.hd hashes2 in
+  let injected =
+    wait_for_injecting_event ~tags:["add_messages"] sc_rollup_node
+  in
+  let* () = Client.bake_for_and_wait client in
+  let* _ = injected in
+  let*! _msg1, status_msg1 =
+    Sc_rollup_client.get_batcher_msg sc_rollup_client hash1
+  in
+  check_status status_msg1 "injected" ;
+  let*! _msg1, status_msg2 =
+    Sc_rollup_client.get_batcher_msg sc_rollup_client hash2
+  in
+  check_status status_msg2 "injected" ;
+  unit
+
 let register ~kind ~protocols =
   test_origination ~kind protocols ;
   test_rollup_node_running ~kind protocols ;
@@ -5376,6 +5419,7 @@ let register ~protocols =
   test_valid_dispute_dissection ~kind:"arith" protocols ;
   test_refutation_reward_and_punishment protocols ~kind:"arith" ;
   test_timeout ~kind:"arith" protocols ;
+  test_inject_identital_messages ~kind:"arith" protocols ;
   test_no_cementation_if_parent_not_lcc_or_if_disputed_commit
     ~kind:"arith"
     protocols ;