diff -r 762ea8a1f5e7 -r a7e49a5b3e6f mercurial/configitems.py
--- a/mercurial/configitems.py	Mon Oct 30 17:09:29 2017 +0100
+++ b/mercurial/configitems.py	Wed Nov 01 17:08:33 2017 +0100
@@ -376,7 +376,7 @@
     default=None,
 )
 coreconfigitem('experimental', 'evolution.effect-flags',
-    default=False,
+    default=True,
     alias=[('experimental', 'effect-flags')]
 )
 coreconfigitem('experimental', 'evolution.exchange',