diff --git a/qt.py b/qt.py
index 0645718..0d0cbaa 100644
--- a/qt.py
+++ b/qt.py
@@ -152,7 +152,7 @@ class Plugin(BalPlugin):
     def get_window(self, window):
         w = self.bal_windows.get(window.winId, None)
         if w is None:
-            win=window.top_level_window()
+            win=w.top_level_window()
             w = BalWindow(self, win)
             self.bal_windows[win.winId] = w
         return w