--- a/mercurial/configitems.py	Sun Jan 14 23:59:17 2018 -0800
+++ b/mercurial/configitems.py	Sun Jan 14 00:02:40 2018 -0800
@@ -487,6 +487,9 @@
 coreconfigitem('experimental', 'evolution.bundle-obsmarker',
     default=False,
 )
+coreconfigitem('experimental', 'evolution.report-instabilities',
+    default=True,
+)
 coreconfigitem('experimental', 'evolution.track-operation',
     default=True,
 )