diff --git a/clutter/clutter-actor.c b/clutter/clutter-actor.c
index 741c66f8c..7300f516d 100644
--- a/clutter/clutter-actor.c
+++ b/clutter/clutter-actor.c
@@ -2065,7 +2065,7 @@ _clutter_actor_get_relative_modelview (ClutterActor *self,
 
 /* Project the given @box into stage window coordinates, writing the
  * transformed vertices to @verts[]. */
-gboolean
+static gboolean
 _clutter_actor_transform_and_project_box (ClutterActor          *self,
 					  const ClutterActorBox *box,
 					  ClutterVertex          verts[])
diff --git a/clutter/clutter-private.h b/clutter/clutter-private.h
index a7725dbda..d955bf931 100644
--- a/clutter/clutter-private.h
+++ b/clutter/clutter-private.h
@@ -463,10 +463,6 @@ void _clutter_actor_set_enable_paint_unmapped (ClutterActor *self,
 void _clutter_actor_set_has_pointer (ClutterActor *self,
                                      gboolean      has_pointer);
 
-gboolean _clutter_actor_transform_and_project_box (ClutterActor          *self,
-                                                   const ClutterActorBox *box,
-                                                   ClutterVertex          verts[]);
-
 void _clutter_actor_queue_redraw_with_clip (ClutterActor          *self,
                                             ClutterRedrawFlags     flags,
                                             ClutterPaintVolume    *clip_volume);