diff --git a/mercurial/httprepo.py b/mercurial/httprepo.py
--- a/mercurial/httprepo.py
+++ b/mercurial/httprepo.py
@@ -71,6 +71,7 @@ def netlocunsplit(host, port, user=None,
 
 class httprepository(remoterepository):
     def __init__(self, ui, path):
+        self.capabilities = ()
         scheme, netloc, urlpath, query, frag = urlparse.urlsplit(path)
         if query or frag:
             raise util.Abort(_('unsupported URL component: "%s"') %
@@ -234,5 +235,8 @@ class httprepository(remoterepository):
 
         return util.chunkbuffer(zgenerator(util.filechunkiter(f)))
 
+    def unbundle(self, cg, heads, source):
+        raise util.Abort(_('operation not supported over http'))
+
 class httpsrepository(httprepository):
     pass