--- a/mercurial/configitems.py	Wed Jan 15 15:47:12 2020 +0100
+++ b/mercurial/configitems.py	Wed Jan 15 15:47:21 2020 +0100
@@ -660,6 +660,9 @@
     b'experimental', b'rust.index', default=False,
 )
 coreconfigitem(
+    b'experimental', b'exp-persistent-nodemap', default=False,
+)
+coreconfigitem(
     b'experimental', b'server.filesdata.recommended-batch-size', default=50000,
 )
 coreconfigitem(