--- a/hgext/evolve.py	Fri Feb 06 16:58:42 2015 +0000
+++ b/hgext/evolve.py	Fri Feb 06 17:01:28 2015 +0000
@@ -2769,6 +2769,23 @@
 
 _bestformat = max(obsolete.formats.keys())
 
+
+if getattr(obsolete, '_checkinvalidmarkers', None) is not None:
+    @eh.wrapfunction(obsolete, '_checkinvalidmarkers')
+    def _checkinvalidmarkers(orig, markers):
+        """search for marker with invalid data and raise error if needed
+
+        Exist as a separated function to allow the evolve extension for a more
+        subtle handling.
+        """
+        if 'debugobsconvert' in sys.argv:
+            return
+        for mark in markers:
+            if node.nullid in mark[1]:
+                raise util.Abort(_('bad obsolescence marker detected: '
+                                   'invalid successors nullid'),
+                                 hint=_('You should run `hg debugobsconvert`'))
+
 @command(
     'debugobsconvert',
     [('', 'new-format', _bestformat, _('Destination format for markers.'))],
@@ -2782,6 +2799,11 @@
     known = set()
     markers = []
     for m in origmarkers:
+        # filter out invalid markers
+        if nullid in m[1]:
+            m = list(m)
+            m[1] = tuple(s for s in m[1] if s != nullid)
+            m = tuple(m)
         if m in known:
             continue
         known.add(m)