--- a/mercurial/configitems.py	Fri Jun 30 01:47:49 2017 +0900
+++ b/mercurial/configitems.py	Sat Jul 01 20:16:54 2017 +0200
@@ -78,7 +78,7 @@
     default='',
 )
 coreconfigitem('devel', 'serverrequirecert',
-    default=None,
+    default=False,
 )
 coreconfigitem('devel', 'strip-obsmarkers',
     default=True,