diff --git a/gdk/gdkinternals.h b/gdk/gdkinternals.h
index 8bed38199b..143ed59529 100644
--- a/gdk/gdkinternals.h
+++ b/gdk/gdkinternals.h
@@ -228,8 +228,6 @@ void _gdk_display_set_surface_under_pointer (GdkDisplay *display,
                                              GdkDevice  *device,
                                              GdkSurface  *surface);
 
-GdkSurface * gdk_surface_get_impl_surface (GdkSurface *surface);
-
 void gdk_surface_destroy_notify       (GdkSurface *surface);
 
 void gdk_synthesize_surface_state (GdkSurface     *surface,