diff -r 18a3274ed675 -r 96802496ecc0 mercurial/obsolete.py
--- a/mercurial/obsolete.py	Sun Oct 08 20:37:13 2017 +0200
+++ b/mercurial/obsolete.py	Sun Oct 08 22:22:27 2017 +0200
@@ -1049,8 +1049,7 @@
 
     # Effect flag metadata handling
     saveeffectflag = repo.ui.configbool('experimental',
-                                        'effect-flags',
-                                        False)
+                                        'effect-flags')
 
     tr = repo.transaction('add-obsolescence-marker')
     try: