diff --git a/lass/1systems/coaxmetal/source.nix b/lass/1systems/coaxmetal/source.nix
index 0e2628b5b..7f335ec05 100644
--- a/lass/1systems/coaxmetal/source.nix
+++ b/lass/1systems/coaxmetal/source.nix
@@ -1,4 +1,21 @@
-{ lib, pkgs, ... }:
-{
-  nixpkgs.git.ref = lib.mkForce (lib.importJSON ../../../krebs/nixpkgs-unstable.json).rev;
+{ lib, pkgs, test, ... }: let
+  npkgs = lib.importJSON ../../../krebs/nixpkgs-unstable.json;
+in {
+  nixpkgs = lib.mkForce (if test then { derivation = let
+    rev = npkgs.rev;
+    sha256 = npkgs.sha256;
+  in ''
+    with import (builtins.fetchTarball {
+      url = "https://github.com/nixos/nixpkgs/archive/${rev}.tar.gz";
+      sha256 = "${sha256}";
+    }) {};
+    pkgs.fetchFromGitHub {
+      owner = "nixos";
+      repo = "nixpkgs";
+      rev = "${rev}";
+      sha256 = "${sha256}";
+    }
+  ''; } else {
+    git.ref = npkgs.rev;
+  });
 }
diff --git a/lass/krops.nix b/lass/krops.nix
index 128c9ee04..fe5c00f3d 100644
--- a/lass/krops.nix
+++ b/lass/krops.nix
@@ -24,7 +24,7 @@
         };
       };
     }
-    (if (lib.pathExists (./. + "/1systems/${name}/source.nix")) && (! test) then
+    (if lib.pathExists (./. + "/1systems/${name}/source.nix") then
       import (./. + "/1systems/${name}/source.nix") { inherit lib pkgs test; }
     else
       {}