diff --git a/src/api/ppx_deriving.cppo.mli b/src/api/ppx_deriving.cppo.mli
index d31e998..da46005 100644
--- a/src/api/ppx_deriving.cppo.mli
+++ b/src/api/ppx_deriving.cppo.mli
@@ -44,6 +44,7 @@ type deriver = {
 
 (** [register deriver] registers [deriver] according to its [name] field. *)
 val register : deriver -> unit
+[@@deprecated]
 
 (** [add_register_hook hook] adds [hook] to be executed whenever a new deriver
     is registered. *)