diff -r 5e111acc1170 -r 51844b8b5017 mercurial/merge.py
--- a/mercurial/merge.py	Thu Apr 30 03:39:39 2015 +0900
+++ b/mercurial/merge.py	Wed Apr 29 15:52:31 2015 -0400
@@ -1167,7 +1167,9 @@
         wlock.release()
 
     if not partial:
-        repo.hook('update', parent1=xp1, parent2=xp2, error=stats[3])
+        def updatehook(parent1=xp1, parent2=xp2, error=stats[3]):
+            repo.hook('update', parent1=parent1, parent2=parent2, error=error)
+        repo._afterlock(updatehook)
     return stats
 
 def graft(repo, ctx, pctx, labels):