diff --git a/nixos/modules/monitoring/server/grafana-service.nix b/nixos/modules/monitoring/server/grafana-service.nix
index b86efa910084e3d147a4097e8b327ef7070d8e0b..fd4055ee396ab4ea450a102402782045920bc851 100644
--- a/nixos/modules/monitoring/server/grafana-service.nix
+++ b/nixos/modules/monitoring/server/grafana-service.nix
@@ -1,3 +1,15 @@
+# This is the NixOS 21.11 Grafana service definition module
+# with the backported UID setting for data sources, so that
+# we can have the same dashboards in our dev, test and prod
+# environments.
+#
+# The change from nixpkgs 81291cc793cf88bd6eff3fd8512e5eb9d037066c
+# will land in NixOS 22.11.
+#
+# When upgrading PrivateStorageio to 22.05, this file will
+# need an upgrade too.  When upgrading PrivateStorageio to
+# 22.11, it can be removed.
+
 { options, config, lib, pkgs, ... }:
 
 with lib;