diff -r 12bc7f06fc41 -r 6f63c47cbb86 mercurial/merge.py
--- a/mercurial/merge.py	Fri Sep 05 11:34:29 2014 -0700
+++ b/mercurial/merge.py	Fri Sep 05 11:36:20 2014 -0700
@@ -1134,6 +1134,7 @@
         stats = applyupdates(repo, actions, wc, p2, overwrite, labels=labels)
 
         if not partial:
+            repo.dirstate.beginparentchange()
             repo.setparents(fp1, fp2)
             recordupdates(repo, actions, branchmerge)
             # update completed, clear state
@@ -1141,6 +1142,7 @@
 
             if not branchmerge:
                 repo.dirstate.setbranch(p2.branch())
+            repo.dirstate.endparentchange()
     finally:
         wlock.release()