--- a/hgext/evolve.py	Wed Aug 27 10:49:58 2014 +0200
+++ b/hgext/evolve.py	Wed Aug 27 12:02:53 2014 +0200
@@ -2238,7 +2238,8 @@
 def _obshash(repo, nodes):
     hashs = _obsrelsethashtree(repo)
     nm = repo.changelog.nodemap
-    return  [hashs[nm.get(n)][1] for n in nodes]
+    revs = [nm.get(n) for n in nodes]
+    return [r is None and nullid or hashs[r][1] for r in revs]
 
 def srv_obshash(repo, proto, nodes):
     return wireproto.encodelist(_obshash(repo, wireproto.decodelist(nodes)))