diff --git a/tests/wpt/mozilla/tests/css/iframe/overflow.html b/tests/wpt/mozilla/tests/css/iframe/overflow.html
index d78bad27546..9ba47d2c57d 100644
--- a/tests/wpt/mozilla/tests/css/iframe/overflow.html
+++ b/tests/wpt/mozilla/tests/css/iframe/overflow.html
@@ -1,14 +1,6 @@
 <html class="reftest-wait">
 <link rel=match href=overflow_ref.html>
- <body>
-   <iframe src="data:text/html,%3Cdiv%20style%3D%22background%3Agreen%3B%20width%3A%20200px%3B%20height%3A%20200px%3B%22%3E%3C%2Fdiv%3E"
-           style="display: block; width: 108px; height: 108px; border: none">
-  </iframe>
-  <script type="text/javascript">
-    window.onload = function() {
-        document.documentElement.classList.remove("reftest-wait");
-    }
-  </script>
- </div>
-</body>
-</html>
+<iframe src="data:text/html,%3Cdiv%20style%3D%22background%3Agreen%3B%20width%3A%20200px%3B%20height%3A%20200px%3B%22%3E%3C%2Fdiv%3E"
+        style="display: block; width: 108px; height: 108px; border: none"
+        onload="document.documentElement.classList.remove('reftest-wait')">
+</iframe>
diff --git a/tests/wpt/mozilla/tests/css/iframe/stacking_context.html b/tests/wpt/mozilla/tests/css/iframe/stacking_context.html
index 54e2b584c3c..67ea2432baa 100644
--- a/tests/wpt/mozilla/tests/css/iframe/stacking_context.html
+++ b/tests/wpt/mozilla/tests/css/iframe/stacking_context.html
@@ -1,4 +1,5 @@
 <!DOCTYPE html>
+<html class=reftest-wait>
 <link rel=match href=stacking_context_ref.html>
 <style>
 iframe {
@@ -11,4 +12,6 @@ iframe {
     transform: translateX(0px); /* form a stacking context */
 }
 </style>
-<iframe src="data:text/html,%3Cspan%3EJust%20a%20simple%20little%20iframe.%3C%2Fspan%3E">
+<iframe src="data:text/html,%3Cspan%3EJust%20a%20simple%20little%20iframe.%3C%2Fspan%3E"
+        onload="document.documentElement.classList.remove('reftest-wait')">
+</iframe>
