diff --git a/src/proto_alpha/lib_protocol/issuance_bonus_repr.ml b/src/proto_alpha/lib_protocol/issuance_bonus_repr.ml
index 231d35277f35d1a2c21a906c07aecedb1ec7a031..2041382517524a897702306689aaf54fe9da325c 100644
--- a/src/proto_alpha/lib_protocol/issuance_bonus_repr.ml
+++ b/src/proto_alpha/lib_protocol/issuance_bonus_repr.ml
@@ -64,9 +64,3 @@ let max_bonus_parameter_of_Q_exn q =
   | Some max_bonus -> max_bonus
   | None ->
       failwith "Invalid parameter: max_bonus parameter must be between 0 and 1"
-
-let migrate_max_bonus_from_O_to_P i =
-  let open Result_syntax in
-  match of_int64_repr i with
-  | Some max_bonus -> return max_bonus
-  | None -> tzfail Out_of_bounds_bonus
diff --git a/src/proto_alpha/lib_protocol/issuance_bonus_repr.mli b/src/proto_alpha/lib_protocol/issuance_bonus_repr.mli
index e54f1b1ef86f28846edb2341959463264d055254..e45bf1727a253ab0d2e94befad0f8f17dcea3270 100644
--- a/src/proto_alpha/lib_protocol/issuance_bonus_repr.mli
+++ b/src/proto_alpha/lib_protocol/issuance_bonus_repr.mli
@@ -36,5 +36,3 @@ val of_Q : max_bonus:max_bonus -> Q.t -> t tzresult
 
 (** Use only to define the [max_bonus] parameter from [Default_parameters]. *)
 val max_bonus_parameter_of_Q_exn : Q.t -> max_bonus
-
-val migrate_max_bonus_from_O_to_P : int64 -> max_bonus tzresult
diff --git a/src/proto_alpha/lib_protocol/raw_context.ml b/src/proto_alpha/lib_protocol/raw_context.ml
index 45db85c3670ccfca4b95dc40ab349bb5b94006fc..1dc5c62ec51a23b271372959d461ba41f5fe628e 100644
--- a/src/proto_alpha/lib_protocol/raw_context.ml
+++ b/src/proto_alpha/lib_protocol/raw_context.ml
@@ -967,9 +967,8 @@ let prepare_first_block ~level ~timestamp _chain_id ctxt =
         return result
     | Oxford_018 ->
         let*! c = get_previous_protocol_constants ctxt in
-        let*? max_bonus =
-          Issuance_bonus_repr.migrate_max_bonus_from_O_to_P
-            c.adaptive_issuance.adaptive_rewards_params.max_bonus
+        let max_bonus =
+          Issuance_bonus_repr.max_bonus_parameter_of_Q_exn Q.(5 // 100)
         in
 
         let cryptobox_parameters =