--- a/mercurial/configitems.py	Tue Apr 14 03:20:21 2020 +0200
+++ b/mercurial/configitems.py	Tue Apr 14 04:23:20 2020 +0200
@@ -663,9 +663,6 @@
     b'experimental', b'rust.index', default=False,
 )
 coreconfigitem(
-    b'experimental', b'exp-persistent-nodemap.mode', default=b'compat',
-)
-coreconfigitem(
     b'experimental', b'server.filesdata.recommended-batch-size', default=50000,
 )
 coreconfigitem(
@@ -1083,6 +1080,10 @@
 coreconfigitem(
     b'storage', b'revlog.nodemap.mmap', default=True, experimental=True
 )
+# experimental as long as format.use-persistent-nodemap is.
+coreconfigitem(
+    b'storage', b'revlog.nodemap.mode', default=b'compat', experimental=True
+)
 coreconfigitem(
     b'storage', b'revlog.reuse-external-delta', default=True,
 )