--- a/gtk/gtkwindow.c
@@ -4351,9 +4351,7 @@
 gboolean
 gtk_window_get_decorated (GtkWindow *window)
 {
-  g_return_val_if_fail (GTK_IS_WINDOW (window), TRUE);
-
-  return window->priv->decorated;
+  return FALSE;
 }
 
 /**