diff --git a/default.nix b/default.nix
index 2ff7811..d8ce6cc 100644
--- a/default.nix
+++ b/default.nix
@@ -16,12 +16,7 @@ let
   toolchainOverlay = import ./toolchain-overlay;
   # Overlay of toolchain patches
 
-  nixpkgs' = builtins.fetchGit {
-    # A branch of Nixpkgs with a custom "crossSystem" mechanism
-    url = "https://github.com/ehmry/nixpkgs.git";
-    ref = "hybrid-19.09";
-    rev = "9a704b7def9bc9ea04d12d6a0d55ebebe0af982a";
-  };
+  nixpkgs' = import ./nixpkgs.nix;
 
 in { nixpkgs ? nixpkgs', dhall-haskell ? ./dhall-haskell.nix }:
 
diff --git a/nixpkgs.nix b/nixpkgs.nix
new file mode 100644
index 0000000..e5b710b
--- /dev/null
+++ b/nixpkgs.nix
@@ -0,0 +1,6 @@
+# A branch of Nixpkgs with a custom "crossSystem" mechanism
+builtins.fetchGit {
+  url = "https://github.com/ehmry/nixpkgs.git";
+  ref = "hybrid-19.09";
+  rev = "9a704b7def9bc9ea04d12d6a0d55ebebe0af982a";
+}
diff --git a/tests/default.nix b/tests/default.nix
index f399fc3..42cbe9d 100644
--- a/tests/default.nix
+++ b/tests/default.nix
@@ -10,21 +10,24 @@ let
     signal = call ./signal.nix { };
     solo5 = call ./solo5.nix { };
   };
-in { pkgs ? (import ./.. { }) }:
+  nixpkgs' = import ./../nixpkgs.nix;
+in { nixpkgs ? nixpkgs' }:
 
 let
+  hostPkgs = import nixpkgs { };
+  testPkgs = import ./.. { inherit nixpkgs; };
 
-  lib = pkgs.buildPackages.pkgs.lib // {
+  lib = hostPkgs.lib // {
 
     renderDhallInit = path: args:
-      pkgs.buildPackages.runCommand "init.xml" {
-        buildInputs = with pkgs.buildPackages; [ linux-dhall ];
+      hostPkgs.runCommand "init.xml" {
+        buildInputs = [ testPkgs.buildPackages.linux-dhall ];
         initConfig = path;
         initArgs = args;
-        DHALL_PRELUDE = "${pkgs.dhallPackages.prelude}/package.dhall";
-        DHALL_GENODE = "${pkgs.dhallPackages.genode}/package.dhall";
+        DHALL_PRELUDE = "${testPkgs.dhallPackages.prelude}/package.dhall";
+        DHALL_GENODE = "${testPkgs.dhallPackages.genode}/package.dhall";
       } ''
-        set -v
+        export XDG_CACHE_HOME=$NIX_BUILD_TOP
         echo 'let Prelude = env:DHALL_GENODE in Prelude.Init.render (Prelude.Init.defaults ⫽ { children =  toMap (env:initConfig env:initArgs) })' \
           | dhall text \
           > $out
@@ -33,5 +36,6 @@ let
   };
 
 in {
-  linux = tests (import ./driver-linux.nix { inherit pkgs lib; }).callTest;
+  linux = tests
+    (import ./driver-linux.nix { inherit testPkgs hostPkgs lib; }).callTest;
 }
diff --git a/tests/driver-linux.nix b/tests/driver-linux.nix
index dba5502..b428204 100644
--- a/tests/driver-linux.nix
+++ b/tests/driver-linux.nix
@@ -2,10 +2,10 @@
 #
 # SPDX-License-Identifier: LicenseRef-Hippocratic-1.1
 
-{ pkgs, lib }:
+{ testPkgs, hostPkgs, lib }:
 
 let
-  testDriver = with pkgs.buildPackages;
+  testDriver = with hostPkgs;
     stdenv.mkDerivation {
       name = "genode-test-driver";
 
@@ -23,7 +23,7 @@ let
     };
 
   runTests = driver:
-    pkgs.stdenv.mkDerivation {
+    hostPkgs.stdenv.mkDerivation {
       name = "test-run-${driver.testName}";
 
       buildCommand = ''
@@ -39,7 +39,7 @@ let
   makeTest = { testScript, testConfig, name ? "unamed", ... }@t:
     let
 
-      baseSetup = with pkgs; ''
+      baseSetup = with testPkgs; ''
         file link -s core ${depot.base-linux}/bin/core
         file link -s timer ${depot.base-linux}/bin/timer
         file link -s ld.lib.so ${depot.base-linux}/lib/ld.lib.so
@@ -48,22 +48,23 @@ let
         file link -s test.config $env(testConfig)
       '';
 
-      driver = pkgs.buildPackages.runCommand "genode-test-driver-${name}" {
-        buildInputs = with pkgs.buildPackages; [ makeWrapper expect ];
-        inherit baseSetup testConfig testScript;
-        preferLocalBuild = true;
-        testName = name;
-      } ''
-        mkdir -p $out/bin
-        echo "$testConfig" > $out/test.config
-        echo "$testScript" > $out/test-script
-        echo "$baseSetup" > $out/base-setup
-        ln -s ${testDriver}/bin/genode-test-driver $out/bin/
-        wrapProgram $out/bin/genode-test-driver \
-          --run "export testConfig=\"$testConfig\"" \
-          --run "export testScript=\"\$(cat $out/test-script)\"" \
-          --run "export baseSetup=\"\$(cat $out/base-setup)\"" \
-      '';
+      driver = with hostPkgs;
+        runCommand "genode-test-driver-${name}" {
+          buildInputs = [ makeWrapper expect ];
+          inherit baseSetup testConfig testScript;
+          preferLocalBuild = true;
+          testName = name;
+        } ''
+          mkdir -p $out/bin
+          echo "$testConfig" > $out/test.config
+          echo "$testScript" > $out/test-script
+          echo "$baseSetup" > $out/base-setup
+          ln -s ${testDriver}/bin/genode-test-driver $out/bin/
+          wrapProgram $out/bin/genode-test-driver \
+            --run "export testConfig=\"$testConfig\"" \
+            --run "export testScript=\"\$(cat $out/test-script)\"" \
+            --run "export baseSetup=\"\$(cat $out/base-setup)\"" \
+        '';
 
       passMeta = drv:
         drv
@@ -74,5 +75,9 @@ let
     in test // { inherit driver test; };
 
 in {
-  callTest = path: args: makeTest (import path ({ inherit pkgs lib; } // args));
+  callTest = path: args:
+    makeTest (import path ({
+      pkgs = testPkgs;
+      inherit lib;
+    } // args));
 }