diff --git a/tests/mocha/index.html b/tests/mocha/index.html
index 2d51a1b52..d4d403314 100644
--- a/tests/mocha/index.html
+++ b/tests/mocha/index.html
@@ -172,7 +172,7 @@
       <block type="test_field_block"></block>
     </xml>
 
-    <script>
+    <script type="module">
       mocha.run(function(failures) {
         var failureDiv = document.getElementById('failureCount');
         failureDiv.setAttribute('tests_failed', failures);