diff -r 7125225a5287 -r 39f0064a3079 mercurial/exchange.py
--- a/mercurial/exchange.py	Wed Jun 24 12:37:55 2015 -0500
+++ b/mercurial/exchange.py	Tue Apr 07 14:14:27 2015 -0700
@@ -36,7 +36,7 @@
             alg = changegroup.readexactly(fh, 2)
         return changegroup.cg1unpacker(fh, alg)
     elif version.startswith('2'):
-        return bundle2.getunbundler(ui, fh, header=magic + version)
+        return bundle2.getunbundler(ui, fh, magicstring=magic + version)
     else:
         raise util.Abort(_('%s: unknown bundle version %s') % (fname, version))