diff --git a/Tests/LibWeb/Text/input/wpt-import/resources/testharness.js b/Tests/LibWeb/Text/input/wpt-import/resources/testharness.js
index 9c536f88801..d56e05112d0 100644
--- a/Tests/LibWeb/Text/input/wpt-import/resources/testharness.js
+++ b/Tests/LibWeb/Text/input/wpt-import/resources/testharness.js
@@ -9,7 +9,7 @@
     // default timeout is 10 seconds, test can override if needed
     var settings = {
         // Assume we are running tests if the internals object is exposed.
-        output:!window.hasOwnProperty("internals"),
+        output: !(window.internals && window.internals.headless),
         harness_timeout:{
             "normal":150000, // NOTE: Overridden for Ladybird due to slow GCC CI
             "long":300000 // NOTE: Overridden for Ladybird due to slow GCC CI
@@ -4549,7 +4549,7 @@
     AssertionError.prototype = Object.create(Error.prototype);
 
     const get_stack = function() {
-        if (window.internals) {
+        if (window.internals && window.internals.headless) {
             return "(Stack traces disabled in Ladybird test mode)";
         }