diff --git a/lass/1systems/green/source.nix b/lass/1systems/green/source.nix
index da137e064..4acdb0c26 100644
--- a/lass/1systems/green/source.nix
+++ b/lass/1systems/green/source.nix
@@ -1,4 +1,6 @@
-{ lib, pkgs, test, ... }:
-if test then {} else {
+{ lib, pkgs, test, ... }: let
+  npkgs = lib.importJSON ../../../krebs/nixpkgs-unstable.json;
+in if test then {} else {
+  nixpkgs.git.ref = lib.mkForce npkgs.rev;
   nixpkgs-unstable = lib.mkForce { file = "/var/empty"; };
 }