--- a/mercurial/commands.py
+++ b/mercurial/commands.py
@@ -2491,7 +2491,7 @@ def unbundle(ui, repo, fname, **opts):
command.
"""
if os.path.exists(fname):
- f = open(fname)
+ f = open(fname, "rb")
else:
f = urllib.urlopen(fname)
gen = changegroup.readbundle(f, fname)