--- a/mercurial/bundle2.py	Mon Feb 13 15:04:46 2017 -0800
+++ b/mercurial/bundle2.py	Wed Feb 15 11:22:01 2017 -0500
@@ -515,7 +515,7 @@
         """setup core part compression to <alg>"""
         if alg in (None, 'UN'):
             return
-        assert not any(n.lower() == 'Compression' for n, v in self._params)
+        assert not any(n.lower() == 'compression' for n, v in self._params)
         self.addparam('Compression', alg)
         self._compengine = util.compengines.forbundletype(alg)
         self._compopts = compopts