diff -r 4b2a086bee31 -r c4c0502be198 mercurial/ui.py
--- a/mercurial/ui.py	Tue Jan 12 22:20:21 2010 +0100
+++ b/mercurial/ui.py	Wed Jan 13 12:00:06 2010 +0100
@@ -134,6 +134,8 @@
         v = self.config(section, name, None, untrusted)
         if v is None:
             return default
+        if isinstance(v, bool):
+            return v
         if v.lower() not in _booleans:
             raise error.ConfigError(_("%s.%s not a boolean ('%s')")
                                     % (section, name, v))