Index: gtk+/gdk/gdkwindow.c
===================================================================
--- gtk+/gdk/gdkwindow.c	(revision 18802)
+++ gtk+/gdk/gdkwindow.c	(working copy)
@@ -615,7 +615,11 @@ gdk_window_get_toplevel (GdkWindow *wind
 
   obj = (GdkWindowObject *)window;
   while (GDK_WINDOW_TYPE (obj) == GDK_WINDOW_CHILD)
-    obj = (GdkWindowObject *)obj->parent;
+    {
+      obj = (GdkWindowObject *)obj->parent;
+      if (!obj)
+	return NULL;
+    }
   
   return GDK_WINDOW (obj);
 }
@@ -2297,6 +2301,9 @@ gdk_window_is_toplevel_frozen (GdkWindow
 
   toplevel = (GdkWindowObject *)gdk_window_get_toplevel (window);
 
+  if (!toplevel)
+    return FALSE;
+
   return toplevel->update_and_descendants_freeze_count > 0;
 }