--- a/hgext/evolve.py	Tue Jun 23 15:26:51 2015 -0700
+++ b/hgext/evolve.py	Mon Jun 22 12:44:21 2015 -0700
@@ -1370,7 +1370,7 @@
                  obs)
         obs = obs.parents()[0]
         newer = obsolete.successorssets(repo, obs.node())
-    if len(newer) > 1:
+    if len(newer) > 1 or len(newer[0]) > 1:
         raise MultipleSuccessorsError(newer)
 
     return repo[newer[0][0]].rev()