diff --git a/nixos/lib/testing.nix b/nixos/lib/testing.nix
index 58c447c76db..9339ba78ff0 100644
--- a/nixos/lib/testing.nix
+++ b/nixos/lib/testing.nix
@@ -149,6 +149,7 @@ rec {
           { key = "run-in-machine";
             networking.hostName = "client";
             nix.readOnlyStore = false;
+            virtualisation.writableStore = false;
           }
         ];
 
diff --git a/nixos/tests/run-in-machine.nix b/nixos/tests/run-in-machine.nix
index d1102f8d407..a6dfece44a9 100644
--- a/nixos/tests/run-in-machine.nix
+++ b/nixos/tests/run-in-machine.nix
@@ -2,7 +2,16 @@
 
 with import ../lib/testing.nix { inherit system; };
 
-runInMachine {
-  drv = pkgs.hello;
-  machine = { config, pkgs, ... }: { /* services.sshd.enable = true; */ };
-}
+let
+  output = runInMachine {
+    drv = pkgs.hello;
+    machine = { config, pkgs, ... }: { /* services.sshd.enable = true; */ };
+  };
+in pkgs.runCommand "verify-output" { inherit output; } ''
+  if [ ! -e "$output/bin/hello" ]; then
+    echo "Derivation built using runInMachine produced incorrect output:" >&2
+    ls -laR "$output" >&2
+    exit 1
+  fi
+  "$output/bin/hello" > "$out"
+''