diff --git a/tests/wpt/mozilla/tests/css/restyle_hints_state.html b/tests/wpt/mozilla/tests/css/restyle_hints_state.html
index 480d1675bb5..27a56d146a3 100644
--- a/tests/wpt/mozilla/tests/css/restyle_hints_state.html
+++ b/tests/wpt/mozilla/tests/css/restyle_hints_state.html
@@ -29,17 +29,22 @@
      * we're not getting as much test coverage there as we'd like. When we
      * implement attribute-based restyle hints, we can stop dirtying the subtree
      * on attribute modifications, and these tests will start to be more useful.
+     *
+     * Also, note that we use window.onload in order to prevent the restyle
+     * hints to interact with any content appended notifications.
      */
-    window.dummy = 0;
-    var $ = document.getElementById.bind(document);
-    function syncRestyle() { window.dummy += $("fs2").offsetTop; }
-    syncRestyle();
-    $('fs1').disabled = true;
-    syncRestyle();
-    $('fs1').disabled = false;
-    syncRestyle();
-    $('cb').checked = true;
-    syncRestyle();
-    $('fs2').disabled = true;
+    window.onload = function() {
+      window.dummy = 0;
+      var $ = document.getElementById.bind(document);
+      function syncRestyle() { window.dummy += $("fs2").offsetTop; }
+      syncRestyle();
+      $('fs1').disabled = true;
+      syncRestyle();
+      $('fs1').disabled = false;
+      syncRestyle();
+      $('cb').checked = true;
+      syncRestyle();
+      $('fs2').disabled = true;
+    }
   </script>
 </body>