--- a/hgext/inhibit.py	Wed May 20 13:32:32 2015 -0700
+++ b/hgext/inhibit.py	Wed May 20 10:58:32 2015 -0700
@@ -43,7 +43,8 @@
 
         def commit(self, *args, **kwargs):
             newnode = super(obsinhibitedrepo, self).commit(*args, **kwargs)
-            _inhibitmarkers(repo, [newnode])
+            if newnode is not None:
+                _inhibitmarkers(repo, [newnode])
             return newnode
 
     repo.__class__ = obsinhibitedrepo