--- a/mercurial/parsers.c	Tue Aug 11 15:34:10 2015 -0400
+++ b/mercurial/parsers.c	Tue Aug 11 14:53:47 2015 -0400
@@ -1232,9 +1232,7 @@
 release_reachable:
 	Py_XDECREF(reachable);
 bail:
-	val = Py_None;
-	Py_INCREF(Py_None);
-	return val;
+	return NULL;
 }
 
 static PyObject *compute_phases_map_sets(indexObject *self, PyObject *args)