diff -r ec17ddecdf64 -r 0af993732f66 mercurial/hg.py
--- a/mercurial/hg.py	Wed Jun 19 23:05:40 2013 -0700
+++ b/mercurial/hg.py	Fri Jun 28 16:58:31 2013 -0700
@@ -472,6 +472,7 @@
 def clean(repo, node, show_stats=True):
     """forcibly switch the working directory to node, clobbering changes"""
     stats = updaterepo(repo, node, True)
+    util.unlinkpath(repo.join('graftstate'), ignoremissing=True)
     if show_stats:
         _showstats(repo, stats)
     return stats[3] > 0