diff -r 5e3c718692bb -r d688a8d537b9 mercurial/configitems.py
--- a/mercurial/configitems.py	Tue Apr 14 03:27:04 2020 +0200
+++ b/mercurial/configitems.py	Tue Apr 14 03:18:14 2020 +0200
@@ -675,9 +675,6 @@
     b'experimental', b'rust.index', default=False,
 )
 coreconfigitem(
-    b'experimental', b'exp-persistent-nodemap', default=False,
-)
-coreconfigitem(
     b'experimental', b'exp-persistent-nodemap.mmap', default=True,
 )
 coreconfigitem(
@@ -787,6 +784,9 @@
     b'format', b'usestore', default=True,
 )
 coreconfigitem(
+    b'format', b'use-persistent-nodemap', default=False, experimental=True
+)
+coreconfigitem(
     b'format',
     b'exp-use-copies-side-data-changeset',
     default=False,