diff --git a/checks/default.nix b/checks/default.nix
index 4113c534..8ac5cb06 100644
--- a/checks/default.nix
+++ b/checks/default.nix
@@ -8,6 +8,25 @@ let
       modules = [ {
         microvm.hypervisor = "qemu";
       } ];
+    } {
+      id = "qemu-tcg";
+      modules = let
+        # Emulate a different guest system than the host one
+        guestSystem = if "${system}" == "x86_64-linux" then "aarch64-unknown-linux-gnu"
+          else "x86_64-linux";
+      in [
+        {
+          microvm = {
+            hypervisor = "qemu";
+            # Force the CPU to be something else than the current
+            # system, and thus, emulated with qemu's Tiny Code Generator
+            # (TCG)
+            cpu = if "${system}" == "x86_64-linux" then "cortex-a53"
+              else "Westmere";
+          };
+          nixpkgs.crossSystem.config = guestSystem;
+        }
+      ];
     } {
       id = "cloud-hypervisor";
       modules = [ {
diff --git a/checks/startup-shutdown.nix b/checks/startup-shutdown.nix
index 774f9b83..3421f8f2 100644
--- a/checks/startup-shutdown.nix
+++ b/checks/startup-shutdown.nix
@@ -15,9 +15,9 @@ let
         };
         microvm = {
           volumes = [ {
-            label = "var";
-            mountPoint = "/var";
-            image = "var.img";
+            image = "output.img";
+            label = "output";
+            mountPoint = "/output";
             size = 32;
           } ];
           crosvm.pivotRoot = "/build/empty";
@@ -35,7 +35,9 @@ let
                 kvmtool = "reboot";
               }.${config.microvm.hypervisor};
             in ''
-              ${pkgs.coreutils}/bin/uname > /var/OK
+              ${pkgs.coreutils}/bin/uname > /output/kernel-name
+              ${pkgs.coreutils}/bin/uname -m > /output/machine-name
+
               ${exit}
             '';
         };
@@ -53,14 +55,34 @@ builtins.mapAttrs (_: nixos:
     ];
     requiredSystemFeatures = [ "kvm" ];
     meta.timeout = 120;
-  } ''
+  } (let
+    expectedMachineName = (crossSystem:
+      if crossSystem == null then
+        expectedMachineName { config = system; }
+      else if crossSystem.config == "aarch64-unknown-linux-gnu" then
+        "aarch64"
+      else if crossSystem.config == "x86_64-linux" then
+        "x86_64"
+      else throw "unknown machine name (${crossSystem.config})"
+    );
+  in ''
     microvm-run
 
-    7z e var.img OK
-    if [ "$(cat OK)" != "Linux" ] ; then
-      echo Output does not match
+    7z e output.img kernel-name machine-name
+
+    EXPECTED_KERNEL_NAME="Linux"
+    if [ "$(cat kernel-name)" != "$EXPECTED_KERNEL_NAME" ] ; then
+      echo "Kernel does not match (got: $(cat kernel-name); expected: $EXPECTED_KERNEL_NAME)"
+      exit 1
+    fi
+
+    EXPECTED_MACHINE_NAME="${expectedMachineName nixos.config.nixpkgs.crossSystem}"
+    if [ "$(cat machine-name)" != "$EXPECTED_MACHINE_NAME" ] ; then
+      echo "Machine does not match (got: $(cat machine-name); expected: $EXPECTED_MACHINE_NAME)"
       exit 1
     fi
-    cp OK $out
-  ''
+
+    mkdir $out
+    cp {kernel-name,machine-name} $out
+  '')
 ) configs
diff --git a/lib/default.nix b/lib/default.nix
index 0e299cfc..7e3b34d4 100644
--- a/lib/default.nix
+++ b/lib/default.nix
@@ -56,9 +56,9 @@ rec {
         # Mark NOCOW
         chattr +C '${image}' || true
         fallocate -l${toString size}MiB '${image}'
-        mkfs.${fsType} ${pkgs.lib.optionalString (label != null) "-L '${label}'"} '${image}'
+        mkfs.${fsType} ${labelArgument} '${image}'
       fi
-    ''));
+    '')));
 
   buildRunner = import ./runner.nix;
 
diff --git a/lib/runner.nix b/lib/runner.nix
index 263be794..f707a032 100644
--- a/lib/runner.nix
+++ b/lib/runner.nix
@@ -19,23 +19,23 @@ let
   preStart = hypervisorConfig.preStart or microvmConfig.preStart;
   tapMultiQueue = hypervisorConfig.tapMultiQueue or false;
 
-  runScriptBin = pkgs.writeScriptBin "microvm-run" ''
-    #! ${pkgs.runtimeShell} -e
+  runScriptBin = pkgs.buildPackages.writeScriptBin "microvm-run" ''
+    #! ${pkgs.buildPackages.runtimeShell} -e
 
     ${preStart}
-    ${createVolumesScript pkgs microvmConfig.volumes}
+    ${createVolumesScript pkgs.buildPackages microvmConfig.volumes}
     ${lib.optionalString (hypervisorConfig.requiresMacvtapAsFds or false) openMacvtapFds}
 
     exec ${command}
   '';
 
-  shutdownScriptBin = pkgs.writeScriptBin "microvm-shutdown" ''
+  shutdownScriptBin = pkgs.buildPackages.writeScriptBin "microvm-shutdown" ''
     #! ${pkgs.runtimeShell} -e
 
     ${shutdownCommand}
   '';
 
-  balloonScriptBin = pkgs.writeScriptBin "microvm-balloon" ''
+  balloonScriptBin = pkgs.buildPackages.writeScriptBin "microvm-balloon" ''
     #! ${pkgs.runtimeShell} -e
 
     if [ -z "$1" ]; then
@@ -48,7 +48,7 @@ let
   '';
 in
 
-pkgs.runCommand "microvm-${microvmConfig.hypervisor}-${microvmConfig.hostName}"
+pkgs.buildPackages.runCommand "microvm-${microvmConfig.hypervisor}-${microvmConfig.hostName}"
 {
   # for `nix run`
   meta.mainProgram = "microvm-run";