diff --git a/collects/mred/private/wx/gtk/window.rkt b/collects/mred/private/wx/gtk/window.rkt
index 1f929c0d..fc6b99f0 100644
--- a/collects/mred/private/wx/gtk/window.rkt
+++ b/collects/mred/private/wx/gtk/window.rkt
@@ -523,6 +523,8 @@
       (gtk_container_remove (send parent get-client-gtk) gtk)
       (set! parent p)
       (gtk_container_add (send parent get-client-gtk) gtk)
+      (set! save-x 0)
+      (set! save-y 0)
       (g_object_unref gtk))
 
     (define/public (get-top-win) (send parent get-top-win))