diff -r df90f4d6c609 -r 5724aaa99dd6 mercurial/obsolete.py
--- a/mercurial/obsolete.py	Fri Jun 30 13:47:24 2017 +0200
+++ b/mercurial/obsolete.py	Fri Jun 30 15:02:19 2017 +0200
@@ -958,7 +958,7 @@
                 continue # emergency cycle hanging prevention
             seen.add(prec)
             if prec not in newermap:
-                obsutil.successorssets(repo, prec, newermap)
+                obsutil.successorssets(repo, prec, cache=newermap)
             newer = [n for n in newermap[prec] if n]
             if len(newer) > 1:
                 divergent.add(ctx.rev())