diff -r a92ba36a1a9d -r e4dc2b0be056 mercurial/bundle2.py
--- a/mercurial/bundle2.py	Wed Sep 24 21:24:06 2014 -0700
+++ b/mercurial/bundle2.py	Wed Sep 24 21:28:54 2014 -0700
@@ -882,6 +882,7 @@
     Exists to allow extensions (like evolution) to mutate the capabilities.
     """
     caps = capabilities.copy()
+    caps['b2x:changegroup'] = tuple(sorted(changegroup.packermap.keys()))
     if obsolete.isenabled(repo, obsolete.exchangeopt):
         supportedformat = tuple('V%i' % v for v in obsolete.formats)
         caps['b2x:obsmarkers'] = supportedformat