--- a/mercurial/revlog.py
+++ b/mercurial/revlog.py
@@ -491,7 +491,7 @@ class revlog(object):
return d
def start(self, rev):
if rev < 0:
- return nullrev
+ return 0
if self.version != REVLOGV0:
return self.ngoffset(self.index[rev][0])
return self.index[rev][0]