diff -r 2c9c88879ab7 -r fc2d5c0aed7f mercurial/configitems.py
--- a/mercurial/configitems.py	Wed Jan 13 18:33:48 2021 +0100
+++ b/mercurial/configitems.py	Wed Jan 13 23:07:41 2021 +0100
@@ -1797,7 +1797,7 @@
 coreconfigitem(
     b'storage',
     b'revlog.persistent-nodemap.slow-path',
-    default=b"allow",
+    default=b"warn",
     experimental=True,
 )