--- a/mercurial/hg.py	Sun Jun 30 14:56:04 2013 -0500
+++ b/mercurial/hg.py	Sun Jun 30 15:19:39 2013 -0500
@@ -471,6 +471,7 @@
 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