diff --git a/nixos/modules/testing/test-instrumentation.nix b/nixos/modules/testing/test-instrumentation.nix
index 2560c1b2dae..54a376c9560 100644
--- a/nixos/modules/testing/test-instrumentation.nix
+++ b/nixos/modules/testing/test-instrumentation.nix
@@ -98,7 +98,7 @@ let kernel = config.boot.kernelPackages.kernel; in
     networking.usePredictableInterfaceNames = false;
 
     # Make it easy to log in as root when running the test interactively.
-    security.initialRootPassword = "";
+    security.initialRootPassword = mkDefault "";
 
   };