diff --git a/preview.html b/preview.html
index 68c96bc..998b353 100644
--- a/preview.html
+++ b/preview.html
@@ -44,7 +44,7 @@
     </script>
   </head>
   <body>
-    <article id="markdown-body">
+    <article id="markdown-body" class="markdown-body">
       <p>Markdown preview</p>
     </article>
   </body>
