diff --git a/lass/1systems/blue/source.nix b/lass/1systems/blue/source.nix
index a52771a4d..8f748ab8f 100644
--- a/lass/1systems/blue/source.nix
+++ b/lass/1systems/blue/source.nix
@@ -1,20 +1,11 @@
 { lib, pkgs, ... }:
 {
   nixpkgs = lib.mkForce {
-    derivation = let
+    file = toString (pkgs.fetchFromGitHub {
+      owner = "nixos";
+      repo = "nixpkgs";
       rev = (lib.importJSON ../../../krebs/nixpkgs.json).rev;
       sha256 = (lib.importJSON ../../../krebs/nixpkgs.json).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}";
-      }
-    '';
+    });
   };
 }
diff --git a/lass/krops.nix b/lass/krops.nix
index d64454ea5..12652216a 100644
--- a/lass/krops.nix
+++ b/lass/krops.nix
@@ -11,7 +11,7 @@
     {}
   ;
 
-  source = { test }: lib.evalSource [
+  source = { test }: lib.evalSource ([
     (krebs-source { test = test; })
     {
       nixos-config.symlink = "stockholm/lass/1systems/${name}/physical.nix";
@@ -24,8 +24,7 @@
         };
       };
     }
-    host-source
-  ];
+  ] ++ (lib.optional (! test) host-source));
 
 in {