diff -r 53eadcb814fd -r c010cb6fdef7 mercurial/revlog.py
--- a/mercurial/revlog.py	Thu Apr 18 14:28:06 2013 -0700
+++ b/mercurial/revlog.py	Thu Apr 18 16:46:09 2013 +0400
@@ -771,10 +771,6 @@
                 nl = [n for n in nl if hex(n).startswith(id)]
                 if len(nl) > 0:
                     if len(nl) == 1:
-                        if nl[0] == nullid:
-                            # dummy null revision always exists,
-                            # it shouldn't be returned here
-                            return None
                         self._pcache[id] = nl[0]
                         return nl[0]
                     raise LookupError(id, self.indexfile,