--- a/mercurial/merge.py	Sun Oct 15 20:36:29 2017 -0700
+++ b/mercurial/merge.py	Sun Oct 15 20:36:29 2017 -0700
@@ -2001,5 +2001,5 @@
         repo.setparents(repo['.'].node(), pother)
         repo.dirstate.write(repo.currenttransaction())
         # fix up dirstate for copies and renames
-        copies.duplicatecopies(repo, ctx.rev(), pctx.rev())
+        copies.duplicatecopies(repo, repo[None], ctx.rev(), pctx.rev())
     return stats