diff --git a/checks/installation/flake-module.nix b/checks/installation/flake-module.nix
index 89b5074d1..80e04fe29 100644
--- a/checks/installation/flake-module.nix
+++ b/checks/installation/flake-module.nix
@@ -15,6 +15,7 @@
           self.clanModules.single-disk
           (modulesPath + "/testing/test-instrumentation.nix") # we need these 2 modules always to be able to run the tests
           (modulesPath + "/profiles/qemu-guest.nix")
+          ../lib/minify.nix
         ];
         clan.single-disk.device = "/dev/vdb";
 
diff --git a/checks/lib/container-test.nix b/checks/lib/container-test.nix
index 27cb19590..f9771ddad 100644
--- a/checks/lib/container-test.nix
+++ b/checks/lib/container-test.nix
@@ -10,7 +10,9 @@ in
     hostPkgs = pkgs;
     # speed-up evaluation
     defaults = {
-      nix.package = pkgs.nixVersions.latest;
+      imports = [
+        ./minify.nix
+      ];
       documentation.enable = lib.mkDefault false;
       boot.isContainer = true;
 
diff --git a/checks/lib/minify.nix b/checks/lib/minify.nix
new file mode 100644
index 000000000..7edaa346b
--- /dev/null
+++ b/checks/lib/minify.nix
@@ -0,0 +1,7 @@
+{
+  nixpkgs.flake.setFlakeRegistry = false;
+  nixpkgs.flake.setNixPath = false;
+  nix.registry.nixpkgs.to = { };
+  documentation.doc.enable = false;
+  documentation.man.enable = false;
+}
diff --git a/checks/lib/test-base.nix b/checks/lib/test-base.nix
index edde37012..0aef4cac8 100644
--- a/checks/lib/test-base.nix
+++ b/checks/lib/test-base.nix
@@ -8,9 +8,11 @@ in
   hostPkgs = pkgs;
   # speed-up evaluation
   defaults = {
+    imports = [
+      ./minify.nix
+    ];
     documentation.enable = lib.mkDefault false;
     nix.settings.min-free = 0;
-    nix.package = pkgs.nixVersions.latest;
   };
 
   # to accept external dependencies such as disko
diff --git a/lib/build-clan/module.nix b/lib/build-clan/module.nix
index 079a7762c..3951b2085 100644
--- a/lib/build-clan/module.nix
+++ b/lib/build-clan/module.nix
@@ -68,7 +68,7 @@ let
               nixpkgs.hostPlatform = lib.mkIf (system != null) (lib.mkDefault system);
 
               # speeds up nix commands by using the nixpkgs from the host system (especially useful in VMs)
-              nix.registry.nixpkgs.to = {
+              nix.registry.nixpkgs.to = lib.mkDefault {
                 type = "path";
                 path = lib.mkDefault nixpkgs;
               };