diff -r 23783463d720 -r 4a6a337f9c68 mercurial/configitems.py
--- a/mercurial/configitems.py	Sun Oct 08 22:07:21 2017 +0200
+++ b/mercurial/configitems.py	Sun Oct 08 22:07:47 2017 +0200
@@ -278,6 +278,9 @@
 coreconfigitem('experimental', 'graphstyle.missing',
     default=dynamicdefault,
 )
+coreconfigitem('experimental', 'graphstyle.grandparent',
+    default=dynamicdefault,
+)
 coreconfigitem('experimental', 'hook-track-tags',
     default=False,
 )