diff --git a/app.js b/app.js
index 26d655a..180004f 100644
--- a/app.js
+++ b/app.js
@@ -60,9 +60,9 @@ function readMarkdown(md) {
     css: codeBlocks.filter((block) => block.lang === "css"),
   }
   const code = {
-    html: blocks.html.length === 1 ? blocks.html[0].value,
-    js: blocks.html.length === 1 ? blocks.js[0].value,
-    css: blocks.html.length === 1 ? blocks.css[0].value,
+    html: blocks.html.length === 1 ? blocks.html[0].value : undefined,
+    js: blocks.html.length === 1 ? blocks.js[0].value : undefined,
+    css: blocks.html.length === 1 ? blocks.css[0].value : undefined,
   }
 }