diff --git a/src/proto_alpha/lib_protocol/sc_rollup_errors.ml b/src/proto_alpha/lib_protocol/sc_rollup_errors.ml
index 16e43e641ae0d6e21049f6c99a8853f8d67c4e6d..e07643d89171e51d06ec7d060aff8ddc2f902141 100644
--- a/src/proto_alpha/lib_protocol/sc_rollup_errors.ml
+++ b/src/proto_alpha/lib_protocol/sc_rollup_errors.ml
@@ -25,7 +25,6 @@
 (*****************************************************************************)
 
 type error +=
-  | (* `Temporary *) Sc_rollup_already_staked
   | (* `Temporary *) Sc_rollup_disputed
   | (* `Temporary *) Sc_rollup_does_not_exist of Sc_rollup_repr.t
   | (* `Temporary *) Sc_rollup_no_conflict
@@ -106,16 +105,6 @@ let () =
           Some ()
       | _ -> None)
     (fun () -> Sc_rollup_max_number_of_messages_reached_for_commitment_period) ;
-  let description = "Already staked." in
-  register_error_kind
-    `Temporary
-    ~id:"Sc_rollup_already_staked"
-    ~title:"Already staked"
-    ~description
-    ~pp:(fun ppf () -> Format.fprintf ppf "%s" description)
-    Data_encoding.empty
-    (function Sc_rollup_already_staked -> Some () | _ -> None)
-    (fun () -> Sc_rollup_already_staked) ;
   let description = "Attempted to cement a disputed commitment." in
   register_error_kind
     `Temporary
diff --git a/src/proto_alpha/lib_protocol/sc_rollup_stake_storage.ml b/src/proto_alpha/lib_protocol/sc_rollup_stake_storage.ml
index 45f8054adae1fb2b7cc92118de5e6e378276f0d3..03baddb4e56c5876a43c16f3f29ceb3cb3d922f2 100644
--- a/src/proto_alpha/lib_protocol/sc_rollup_stake_storage.ml
+++ b/src/proto_alpha/lib_protocol/sc_rollup_stake_storage.ml
@@ -47,19 +47,17 @@ let modify_staker_count ctxt rollup f =
   assert (Compare.Int.(size_diff = 0)) ;
   return ctxt
 
+(** Warning: must be called only if [rollup] exists and [staker] is not to be
+    found in {!Store.Stakers.} *)
 let deposit_stake ctxt rollup staker =
   let open Lwt_tzresult_syntax in
   let* lcc, ctxt = Commitment_storage.last_cemented_commitment ctxt rollup in
-  let* ctxt, res = Store.Stakers.find (ctxt, rollup) staker in
-  match res with
-  | None ->
-      (* TODO: https://gitlab.com/tezos/tezos/-/issues/2449
-         We should lock stake here, and fail if there aren't enough funds.
-      *)
-      let* ctxt, _size = Store.Stakers.init (ctxt, rollup) staker lcc in
-      let* ctxt = modify_staker_count ctxt rollup Int32.succ in
-      return ctxt
-  | Some _ -> fail Sc_rollup_already_staked
+  (* TODO: https://gitlab.com/tezos/tezos/-/issues/2449
+     We should lock stake here, and fail if there aren't enough funds.
+  *)
+  let* ctxt, _size = Store.Stakers.init (ctxt, rollup) staker lcc in
+  let* ctxt = modify_staker_count ctxt rollup Int32.succ in
+  return ctxt
 
 let withdraw_stake ctxt rollup staker =
   let open Lwt_tzresult_syntax in
@@ -268,12 +266,9 @@ let refine_stake ctxt rollup staker commitment =
 
 let publish_commitment ctxt rollup staker commitment =
   let open Lwt_tzresult_syntax in
-  let* ctxt, res = Store.Stakers.find (ctxt, rollup) staker in
-  match res with
-  | None ->
-      let* ctxt = deposit_stake ctxt rollup staker in
-      refine_stake ctxt rollup staker commitment
-  | Some _ -> refine_stake ctxt rollup staker commitment
+  let* ctxt, res = Store.Stakers.mem (ctxt, rollup) staker in
+  let* ctxt = if res then return ctxt else deposit_stake ctxt rollup staker in
+  refine_stake ctxt rollup staker commitment
 
 (** Try to consume n messages. *)
 let consume_n_messages ctxt rollup n =
diff --git a/src/proto_alpha/lib_protocol/sc_rollup_stake_storage.mli b/src/proto_alpha/lib_protocol/sc_rollup_stake_storage.mli
index 3ce6e4c7055e7e15fc25e6b77352aa600cae0f6a..19979776411b521168113853232a58ad8113e7d6 100644
--- a/src/proto_alpha/lib_protocol/sc_rollup_stake_storage.mli
+++ b/src/proto_alpha/lib_protocol/sc_rollup_stake_storage.mli
@@ -126,10 +126,11 @@ module Internal_for_tests : sig
       cemented commitment, freezing [sc_rollup_deposit] from [staker]'s account
       balance.
 
+      Warning: must be called only if [rollup] exists and [staker] is not to be
+      found in {!Store.Stakers.}
+
       May fail with:
       {ul
-        {li [Sc_rollup_does_not_exist] if [rollup] does not exist}
-        {li [Sc_rollup_already_staked] if [staker] is already staked}
         {li [Sc_rollup_staker_funds_too_low] if [staker] does not have enough
             funds to cover the deposit}
       }
diff --git a/src/proto_alpha/lib_protocol/test/unit/test_sc_rollup_storage.ml b/src/proto_alpha/lib_protocol/test/unit/test_sc_rollup_storage.ml
index 52b4e5734e7a68bdfcb3988e63fa30af486382ab..33e6a1e129cc573a406e32dc3cb11c0488d44134 100644
--- a/src/proto_alpha/lib_protocol/test/unit/test_sc_rollup_storage.ml
+++ b/src/proto_alpha/lib_protocol/test/unit/test_sc_rollup_storage.ml
@@ -227,28 +227,6 @@ let test_deposit_then_withdraw () =
      in
      assert_true ctxt
 
-let test_can_not_stake_twice () =
-  let* ctxt = new_context () in
-  let* rollup, ctxt = lift @@ new_sc_rollup ctxt in
-  let staker =
-    Signature.Public_key_hash.of_b58check_exn
-      "tz1SdKt9kjPp1HRQFkBmXtBhgMfvdgFhSjmG"
-  in
-  let* ctxt =
-    lift
-    @@ Sc_rollup_stake_storage.Internal_for_tests.deposit_stake
-         ctxt
-         rollup
-         staker
-  in
-  assert_fails_with
-    ~loc:__LOC__
-    (Sc_rollup_stake_storage.Internal_for_tests.deposit_stake
-       ctxt
-       rollup
-       staker)
-    "Already staked."
-
 let test_withdrawal_from_missing_rollup () =
   assert_fails_with_missing_rollup ~loc:__LOC__ (fun ctxt rollup ->
       Sc_rollup_stake_storage.Internal_for_tests.withdraw_stake
@@ -2456,7 +2434,6 @@ let tests =
       "deposit to existing rollup"
       `Quick
       test_deposit_to_existing_rollup;
-    Tztest.tztest "can not deposit twice" `Quick test_can_not_stake_twice;
     Tztest.tztest "deposit, then withdraw" `Quick test_deposit_then_withdraw;
     Tztest.tztest
       "cement with zero stakers fails"