diff --git a/flake.nix b/flake.nix
index a8ecae89c..1eedb8bbd 100644
--- a/flake.nix
+++ b/flake.nix
@@ -4,6 +4,10 @@
 {
   inputs = {
     nixpkgs = {
+      # Renovate has some false heuristic to detect whether something can be `nix flake update`ed,
+      # see https://github.com/renovatebot/renovate/issues/29721 and
+      # https://github.com/renovatebot/renovate/blob/743fed0ec6ca5810e274571c83fa6d4f5213d4e7/lib/modules/manager/nix/extract.ts#L6.
+      # We must keep the following string in the file for renovate to work: "github:NixOS/nixpkgs/nixpkgs-unstable"
       url = "github:NixOS/nixpkgs?ref=nixos-unstable";
     };
     flake-utils = {