diff --git a/tests/mocha/index.html b/tests/mocha/index.html
index 3d1cfaa9c..1891821b2 100644
--- a/tests/mocha/index.html
+++ b/tests/mocha/index.html
@@ -26,7 +26,8 @@
     <script src="../../node_modules/sinon/pkg/sinon.js"></script>
     <script>
       mocha.setup({
-        ui: 'tdd'
+        ui: 'tdd',
+        failZero: true,
       });
     </script>