diff -r 86f39a89b63e -r 76608f9f27f6 mercurial/configitems.py
--- a/mercurial/configitems.py	Wed Sep 25 12:57:11 2019 +0200
+++ b/mercurial/configitems.py	Wed Sep 25 12:59:26 2019 +0200
@@ -645,6 +645,9 @@
 coreconfigitem('experimental', 'single-head-per-branch',
     default=False,
 )
+coreconfigitem('experimental', 'single-head-per-branch:account-closed-heads',
+    default=False,
+)
 coreconfigitem('experimental', 'sshserver.support-v2',
     default=False,
 )