diff --git a/hosts/netty/forgejo-runner.nix b/hosts/netty/forgejo-runner.nix
index f4cedeb..688eb79 100644
--- a/hosts/netty/forgejo-runner.nix
+++ b/hosts/netty/forgejo-runner.nix
@@ -5,6 +5,7 @@
 }:
 
 let
+  # Cache root for tooling used inside CI jobs (npm, pip, cargo, ...).
   cacheRoot = "/var/cache/forgejo-runner";
 in
 {