--- a/hgext/evolve.py	Tue Jun 16 10:19:17 2015 -0700
+++ b/hgext/evolve.py	Tue Jun 16 14:30:43 2015 -0700
@@ -1234,12 +1234,12 @@
         ui.status(_('working directory is now at %s\n') % repo['.'])
 
 def _singlesuccessor(repo, p):
-    """returns p if not obsolete or its unique latest successors
+    """returns p (as rev) if not obsolete or its unique latest successors
 
     fail if there are no such successor"""
 
     if not p.obsolete():
-        return p
+        return p.rev()
     obs = repo[p]
     ui = repo.ui
     newer = obsolete.successorssets(repo, obs.node())