diff --git a/Tests/LibWeb/Text/input/wpt-import/resources/testharness.js b/Tests/LibWeb/Text/input/wpt-import/resources/testharness.js
index 9d2d1f0a69a..401f7a6c8ba 100644
--- a/Tests/LibWeb/Text/input/wpt-import/resources/testharness.js
+++ b/Tests/LibWeb/Text/input/wpt-import/resources/testharness.js
@@ -559,7 +559,7 @@
     // Tell the ladybird test runner what our preferred timeout is
     {
         let timeout = test_environment.test_timeout();
-        if (timeout)
+        if (timeout && window.internals)
             window.internals.setTestTimeout(timeout);
     }