diff --git a/packages/demo/src/cms.jsx b/packages/demo/src/cms.jsx
index 5f2dc8c0..6b47afb8 100644
--- a/packages/demo/src/cms.jsx
+++ b/packages/demo/src/cms.jsx
@@ -165,7 +165,6 @@ const CustomPage = () => {
   return <div>I am a custom page!</div>;
 };
 
-cms.registerPreviewStyle(".toastui-editor-contents h1 { color: blue }", { raw: true });
 cms.registerPreviewTemplate("posts", PostPreview);
 CMS.registerPreviewCard("posts", PostPreviewCard);
 CMS.registerFieldPreview('posts', 'date', PostDateFieldPreview);