diff -r c63a09b6b337 -r c136e26953aa mercurial/localrepo.py
--- a/mercurial/localrepo.py	Wed Oct 15 15:35:59 2014 -0400
+++ b/mercurial/localrepo.py	Wed Oct 15 12:52:10 2014 -0700
@@ -405,7 +405,7 @@
         # rely on obsstore class default when possible.
         kwargs = {}
         if defaultformat is not None:
-            defaultformat['defaultformat'] = defaultformat
+            kwargs['defaultformat'] = defaultformat
         store = obsolete.obsstore(self.sopener, **kwargs)
         if store and not obsolete._enabled:
             # message is rare enough to not be translated