diff -r 31fdb04cb5e8 -r 0d3f35394af4 mercurial/extensions.py
--- a/mercurial/extensions.py	Wed Feb 02 23:21:13 2011 +0100
+++ b/mercurial/extensions.py	Thu Feb 10 13:46:27 2011 -0600
@@ -11,6 +11,7 @@
 
 _extensions = {}
 _order = []
+_ignore = ['hbisect']
 
 def extensions():
     for name in _order:
@@ -45,6 +46,8 @@
         shortname = name[6:]
     else:
         shortname = name
+    if shortname in _ignore:
+        return None
     if shortname in _extensions:
         return _extensions[shortname]
     _extensions[shortname] = None