diff --git a/Tools/idle/WindowList.py b/Tools/idle/WindowList.py
index cee435d2f1f..6de3e5855c5 100644
--- a/Tools/idle/WindowList.py
+++ b/Tools/idle/WindowList.py
@@ -39,8 +39,8 @@ def register_callback(self, callback):
 
     def unregister_callback(self, callback):
         try:
-            self.callback.remove(callback)
-        except:
+           self.callbacks.remove(callback)
+        except ValueError:
             pass
 
     def call_callbacks(self):