diff -r 974389427e5f -r e994b034e91e mercurial/localrepo.py
--- a/mercurial/localrepo.py	Thu Oct 09 00:10:10 2014 -0700
+++ b/mercurial/localrepo.py	Tue Sep 16 17:52:40 2014 -0700
@@ -400,7 +400,13 @@
 
     @storecache('obsstore')
     def obsstore(self):
-        store = obsolete.obsstore(self.sopener)
+        # read default format for new obsstore.
+        defaultformat = self.ui.configint('format', 'obsstore-version', None)
+        # rely on obsstore class default when possible.
+        kwargs = {}
+        if defaultformat is not None:
+            defaultformat['defaultformat'] = defaultformat
+        store = obsolete.obsstore(self.sopener, **kwargs)
         if store and not obsolete._enabled:
             # message is rare enough to not be translated
             msg = 'obsolete feature not enabled but %i markers found!\n'