diff --git a/gdk/gdkwindowimpl.c b/gdk/gdkwindowimpl.c
index 48fe438fd8..2c4df30d51 100644
--- a/gdk/gdkwindowimpl.c
+++ b/gdk/gdkwindowimpl.c
@@ -29,19 +29,11 @@
 #include "gdkinternals.h"
 
 
-GType
-gdk_window_impl_get_type (void)
+typedef GdkWindowImplIface GdkWindowImplInterface;
+G_DEFINE_INTERFACE (GdkWindowImpl, gdk_window_impl, G_TYPE_OBJECT);
+
+
+static void
+gdk_window_impl_default_init (GdkWindowImplInterface *iface)
 {
-  static GType gtype = 0;
-
-  if (G_UNLIKELY (!gtype))
-    {
-      gtype = g_type_register_static_simple (G_TYPE_INTERFACE,
-                                             "GdkWindowImpl",
-                                             sizeof (GdkWindowImplIface),
-                                             NULL, 0, NULL, 0);
-      g_type_interface_add_prerequisite (gtype, G_TYPE_OBJECT);
-    }
-
-  return gtype;
 }