--- a/hgext/obsolete.py	Fri Jul 06 18:43:25 2012 +0200
+++ b/hgext/obsolete.py	Tue Jul 10 16:03:29 2012 +0200
@@ -609,7 +609,7 @@
                 del oldmark['id']  # dropped for now
                 del oldmark['reason']  # unused until then
                 oldobject = str(oldmark.pop('object'))
-                oldsubjects = [str(s) for s in oldmark.pop('subjects')]
+                oldsubjects = [str(s) for s in oldmark.pop('subjects', [])]
                 LOOKUP_ERRORS = (error.RepoLookupError, error.LookupError)
                 if len(oldobject) != 40:
                     try:
@@ -626,7 +626,9 @@
                 meta = dict((k.encode('utf-8'), v.encode('utf-8'))
                              for k, v in oldmark.iteritems())
                 try:
-                    store.create(bin(oldobject), [bin(n) for n in oldsubjects],
+                    succs = [bin(n) for n in oldsubjects]
+                    succs = [n for n in succs if n != nullid]
+                    store.create(bin(oldobject), succs,
                                  0, meta)
                     cnt += 1
                 except ValueError: