--- a/hgext/convert/convcmd.py	Fri Apr 27 01:26:23 2018 -0400
+++ b/hgext/convert/convcmd.py	Fri Apr 27 01:27:22 2018 -0400
@@ -234,7 +234,7 @@
     def walktree(self, heads):
         '''Return a mapping that identifies the uncommitted parents of every
         uncommitted changeset.'''
-        visit = heads
+        visit = list(heads)
         known = set()
         parents = {}
         numcommits = self.source.numcommits()