diff -r 9796cf108e4e -r d159d0fafa78 mercurial/configitems.py
--- a/mercurial/configitems.py	Fri Jan 08 21:34:16 2021 +0530
+++ b/mercurial/configitems.py	Fri Jan 08 21:47:31 2021 +0530
@@ -1084,6 +1084,11 @@
 )
 coreconfigitem(
     b'experimental',
+    b'sharesafe-auto-upgrade-fail-error',
+    default=False,
+)
+coreconfigitem(
+    b'experimental',
     b'sharesafe-warn-outdated-shares',
     default=True,
 )