diff -r 9f2c407caf34 -r acbe171c8fbe mercurial/changegroup.py
--- a/mercurial/changegroup.py	Tue Feb 22 03:10:37 2011 +0100
+++ b/mercurial/changegroup.py	Tue Feb 22 16:31:01 2011 +0100
@@ -151,7 +151,7 @@
         return self._stream.close()
 
     def chunklength(self):
-        d = readexactly(stream, 4)
+        d = readexactly(self._stream, 4)
         l = struct.unpack(">l", d)[0]
         if l <= 4:
             if l: