diff -r a31b8e03af28 -r d0424f39984c mercurial/url.py
--- a/mercurial/url.py	Mon Aug 01 14:53:10 2011 -0500
+++ b/mercurial/url.py	Mon Aug 01 18:10:05 2011 -0500
@@ -25,7 +25,7 @@
             self._writedebug(user, passwd)
             return (user, passwd)
 
-        if not user:
+        if not user or not passwd:
             res = httpconnectionmod.readauthforuri(self.ui, authuri)
             if res:
                 group, auth = res