Fix for Issue6111.
diff --git a/Lib/idlelib/macosxSupport.py b/Lib/idlelib/macosxSupport.py
index e759157..b23221e 100644
--- a/Lib/idlelib/macosxSupport.py
+++ b/Lib/idlelib/macosxSupport.py
@@ -82,6 +82,12 @@
def config_dialog(event=None):
from idlelib import configDialog
+
+ # Ensure that the root object has an instance_dict attribute,
+ # mirrors code in EditorWindow (although that sets the attribute
+ # on an EditorWindow instance that is then passed as the first
+ # argument to ConfigDialog)
+ root.instance_dict = flist.inversedict
configDialog.ConfigDialog(root, 'Settings')