--- a/mercurial/merge.py	Tue Oct 13 10:57:54 2015 -0700
+++ b/mercurial/merge.py	Tue Sep 29 01:03:26 2015 -0700
@@ -1027,7 +1027,8 @@
             pas = [repo[ancestor]]
 
         if node is None:
-            node = repo[destutil.destupdate(repo)].node()
+            rev, _mark, _act = destutil.destupdate(repo)
+            node = repo[rev].node()
 
         overwrite = force and not branchmerge