diff -r 2c124e30a324 Lib/idlelib/EditorWindow.py
--- a/Lib/idlelib/EditorWindow.py	Fri Aug 07 00:43:39 2015 -0700
+++ b/Lib/idlelib/EditorWindow.py	Mon Aug 10 14:34:18 2015 -0700
@@ -758,6 +758,19 @@
         self.per.removefilter(self.color)
         self.color = None
 
+
+    def configuration_will_change(self):
+        "Callback from configuration dialog before settings are applied."
+        self.RemoveKeybindings()
+        
+    def configuration_changed(self):
+        "Callback from configuration dialog after settings are applied."
+        self.ResetColorizer()
+        self.ResetFont()
+        self.set_notabs_indentwidth()
+        self.ApplyKeybindings()
+        self.reset_help_menu_entries()
+
     def ResetColorizer(self):
         "Update the color theme"
         # Called from self.filename_change_hook and from configDialog.py
diff -r 2c124e30a324 Lib/idlelib/FileList.py
--- a/Lib/idlelib/FileList.py	Fri Aug 07 00:43:39 2015 -0700
+++ b/Lib/idlelib/FileList.py	Mon Aug 10 14:34:18 2015 -0700
@@ -109,6 +109,16 @@
                 filename = os.path.join(pwd, filename)
         return os.path.normpath(filename)
 
+    def configuration_will_change(self):
+        "Callback from configuration dialog before settings are applied."
+        for w in self.inversedict.keys():
+            w.configuration_will_change()
+        
+    def configuration_changed(self):
+        "Callback from configuration dialog after settings are applied."
+        for w in self.inversedict.keys():
+            w.configuration_changed()
+
 
 def _test():
     from idlelib.EditorWindow import fixwordbreaks
diff -r 2c124e30a324 Lib/idlelib/configDialog.py
--- a/Lib/idlelib/configDialog.py	Fri Aug 07 00:43:39 2015 -0700
+++ b/Lib/idlelib/configDialog.py	Mon Aug 10 14:34:18 2015 -0700
@@ -30,8 +30,16 @@
         """
         Toplevel.__init__(self, parent)
         self.parent = parent
-        if _htest:
-            parent.instance_dict = {}
+        # Hold onto the list of files the parent belongs to, as the parent 
+        # may go away if we're not modal. The file list may not be present 
+        # e.g. if testing where we won't be passed an editor window; to 
+        # prevent an API change we'll try to extract it here, rather than
+        # asking it to be passed to us.
+        try:
+            self.flist = parent.flist
+        except AttributeError:
+            self.flist = None
+
         self.wm_withdraw()
 
         self.configure(borderwidth=5)
@@ -70,6 +78,7 @@
         #self.bind('<F1>', self.Help) #context help
         self.LoadConfigs()
         self.AttachVarCallbacks() #avoid callbacks during LoadConfigs
+        self.parent = None # after start, can't guarantee parent still exists
 
         if not _utest:
             self.wm_deiconify()
@@ -1140,19 +1149,13 @@
     def DeactivateCurrentConfig(self):
         #Before a config is saved, some cleanup of current
         #config must be done - remove the previous keybindings
-        winInstances = self.parent.instance_dict.keys()
-        for instance in winInstances:
-            instance.RemoveKeybindings()
+        if self.flist:
+            self.flist.configuration_will_change()
 
     def ActivateConfigChanges(self):
         "Dynamically apply configuration changes"
-        winInstances = self.parent.instance_dict.keys()
-        for instance in winInstances:
-            instance.ResetColorizer()
-            instance.ResetFont()
-            instance.set_notabs_indentwidth()
-            instance.ApplyKeybindings()
-            instance.reset_help_menu_entries()
+        if self.flist:
+            self.flist.configuration_changed()
 
     def Cancel(self):
         self.destroy()
diff -r 2c124e30a324 Lib/idlelib/macosxSupport.py
--- a/Lib/idlelib/macosxSupport.py	Fri Aug 07 00:43:39 2015 -0700
+++ b/Lib/idlelib/macosxSupport.py	Mon Aug 10 14:34:18 2015 -0700
@@ -171,6 +171,7 @@
         # argument to ConfigDialog)
         root.instance_dict = flist.inversedict
         root.instance_dict = flist.inversedict
+        root.flist = flist
         configDialog.ConfigDialog(root, 'Settings')
 
     def help_dialog(event=None):