diff --git a/src/proto_alpha/lib_protocol/script_ir_translator.ml b/src/proto_alpha/lib_protocol/script_ir_translator.ml
index 4f987a86ea9e37530283d00ceed79e053e2f27d5..ea3d29b5e7e00f0462321073f725db54d4670c1d 100644
--- a/src/proto_alpha/lib_protocol/script_ir_translator.ml
+++ b/src/proto_alpha/lib_protocol/script_ir_translator.ml
@@ -607,9 +607,13 @@ let rec parse_ty :
     | Prim (loc, T_key_hash, [], annot) ->
         check_type_annot loc annot >|? fun () -> return ctxt key_hash_t
     | Prim (loc, T_chest_key, [], annot) ->
-        check_type_annot loc annot >|? fun () -> return ctxt chest_key_t
+        if legacy then
+          check_type_annot loc annot >|? fun () -> return ctxt chest_key_t
+        else error (Deprecated_instruction T_chest_key)
     | Prim (loc, T_chest, [], annot) ->
-        check_type_annot loc annot >|? fun () -> return ctxt chest_t
+        if legacy then
+          check_type_annot loc annot >|? fun () -> return ctxt chest_t
+        else error (Deprecated_instruction T_chest)
     | Prim (loc, T_timestamp, [], annot) ->
         check_type_annot loc annot >|? fun () -> return ctxt timestamp_t
     | Prim (loc, T_address, [], annot) ->
diff --git a/src/proto_alpha/lib_protocol/test/integration/michelson/test_timelock.ml b/src/proto_alpha/lib_protocol/test/integration/michelson/test_timelock.ml
index 4f0ac0df7bca47364af7a62193fd5791d6792a45..7e548766f55d9d0f39ff06c8cae1d1c475bc88da 100644
--- a/src/proto_alpha/lib_protocol/test/integration/michelson/test_timelock.ml
+++ b/src/proto_alpha/lib_protocol/test/integration/michelson/test_timelock.ml
@@ -72,7 +72,7 @@ let deprecated_chest_open () =
     when List.mem
            ~equal:( = )
            (Environment.Ecoproto_error
-              (Script_tc_errors.Deprecated_instruction I_OPEN_CHEST))
+              (Script_tc_errors.Deprecated_instruction T_chest_key))
            lst ->
       return ()
   | Error errs ->