diff --git a/source/importing-css-assets-and-javascript/index.html.md.erb b/source/importing-css-assets-and-javascript/index.html.md.erb
index 59e4ab85..7e070cb1 100644
--- a/source/importing-css-assets-and-javascript/index.html.md.erb
+++ b/source/importing-css-assets-and-javascript/index.html.md.erb
@@ -184,7 +184,10 @@ Then import the JavaScript file before the closing `</body>` tag of your HTML pa
 
 ```html
 <body class="govuk-template__body">
+  <script>document.body.className += ' js-enabled' + ('noModule' in HTMLScriptElement.prototype ? ' govuk-frontend-supported' : '');</script>
+
   <!-- // ... -->
+
   <script type="module" src="<YOUR-JAVASCRIPTS-FOLDER>/govuk-frontend.min.js"></script>
   <script type="module">
     import { initAll } from '<YOUR-JAVASCRIPTS-FOLDER>/govuk-frontend.min.js'
