diff --git a/doc/release-notes/rl-2505.section.md b/doc/release-notes/rl-2505.section.md
index 11d54b19159f..6e059a00136f 100644
--- a/doc/release-notes/rl-2505.section.md
+++ b/doc/release-notes/rl-2505.section.md
@@ -427,6 +427,8 @@
   add `vimPlugins.notmuch-vim` to your (Neo)vim configuration if you want the
   vim plugin.
 
+- The fileSystems (e.g., `fileSystems."/"`) are now set by NixOS-implemented modules using `lib.mkDefault`, allowing wholesale overrides, but this means that overriding individual attributes (like `fsType` or `options`) without explicitly specifying `device` may result in missing required fields and errors such as `No device specified for mount point '/'` (https://github.com/NixOS/nixpkgs/pull/377406).
+
 - `prisma` and `prisma-engines` have been updated to version 6.7.0, which
   introduces several breaking changes. See the
   [Prisma ORM upgrade guide](https://www.prisma.io/docs/orm/more/upgrade-guides/upgrading-versions/upgrading-to-prisma-6)