--- a/mercurial/configitems.py	Sun Oct 08 20:37:13 2017 +0200
+++ b/mercurial/configitems.py	Sun Oct 08 22:22:27 2017 +0200
@@ -348,6 +348,9 @@
 coreconfigitem('experimental', 'nonnormalparanoidcheck',
     default=False,
 )
+coreconfigitem('experimental', 'effect-flags',
+    default=False,
+)
 coreconfigitem('experimental', 'stabilization',
     default=list,
     alias=[('experimental', 'evolution')],