diff --git a/testing/marionette/.eslintrc.js b/testing/marionette/.eslintrc.js
index 966f2a5be7ef..4b21d91fc193 100644
--- a/testing/marionette/.eslintrc.js
+++ b/testing/marionette/.eslintrc.js
@@ -17,6 +17,7 @@ module.exports = {
     "no-fallthrough": "error",
     "no-new-object": "error",
     "no-undef-init": "error",
+    "no-var": "error",
     "object-curly-spacing": ["error", "never"],
     "semi": "error",
   }