diff -r 31c0ee6eb0ac -r b17d27ea61fb mercurial/phases.py
--- a/mercurial/phases.py	Thu Aug 23 01:48:26 2018 +0200
+++ b/mercurial/phases.py	Thu Aug 23 01:48:39 2018 +0200
@@ -599,7 +599,7 @@
     # to update. This avoid creating empty transaction during no-op operation.
 
     for phase in allphases[:-1]:
-        revset = '%%ln - %s()' % phasenames[phase]
+        revset = '%%ln - _phase(%d)' % phase
         heads = [c.node() for c in repo.set(revset, headsbyphase[phase])]
         if heads:
             advanceboundary(repo, trgetter(), phase, heads)