diff --git a/step1-04/demo/index.html b/step1-04/demo/index.html
index 2d3fc449..f6bacbc5 100644
--- a/step1-04/demo/index.html
+++ b/step1-04/demo/index.html
@@ -21,7 +21,7 @@
   background: green;
 }
     </pre>
-    <pre data-lang="javascript">
+    <pre data-lang="typescript">
 ReactDOM.render(
   &lt;div>Hello World&lt;/div>, 
   document.getElementById('app')