diff -r f78eadbb5769 -r f9a80054dd3c mercurial/ui.py
--- a/mercurial/ui.py	Wed May 20 00:43:23 2009 +0200
+++ b/mercurial/ui.py	Wed May 20 00:52:46 2009 +0200
@@ -129,7 +129,7 @@
 
     def configbool(self, section, name, default=False, untrusted=False):
         v = self.config(section, name, None, untrusted)
-        if v == None:
+        if v is None:
             return default
         if v.lower() not in _booleans:
             raise error.ConfigError(_("%s.%s not a boolean ('%s')")