diff -r 2959c3e986e0 -r bd872f64a8ba mercurial/discovery.py
--- a/mercurial/discovery.py	Sat May 06 04:51:25 2017 +0530
+++ b/mercurial/discovery.py	Fri Feb 10 16:56:29 2017 -0800
@@ -254,7 +254,7 @@
     newheads = list(c.node() for c in r)
     # set some unsynced head to issue the "unsynced changes" warning
     if inc:
-        unsynced = set([None])
+        unsynced = {None}
     else:
         unsynced = set()
     return {None: (oldheads, newheads, unsynced)}