--- a/mercurial/util.py
+++ b/mercurial/util.py
@@ -1421,7 +1421,7 @@ class chunkbuffer(object):
self.iter = False
self.buf = collector.getvalue()
if len(self.buf) == l:
- s, self.buf = self.buf, ''
+ s, self.buf = str(self.buf), ''
else:
s, self.buf = self.buf[:l], buffer(self.buf, l)
return s