diff --git a/testing/web-platform/tests/quirks/unitless-length/no-quirks.html b/testing/web-platform/tests/quirks/unitless-length/no-quirks.html
index cd192029df49..82036f9a6170 100644
--- a/testing/web-platform/tests/quirks/unitless-length/no-quirks.html
+++ b/testing/web-platform/tests/quirks/unitless-length/no-quirks.html
@@ -2,6 +2,7 @@
 <html>
  <head>
   <title>The unitless length quirk (no-quirks)</title>
+  <meta name="timeout" content="long">
   <script src="/resources/testharness.js"></script>
   <script src="/resources/testharnessreport.js"></script>
   <style> iframe { width:20px; height:20px; } </style>
