diff --git a/src/node/plugin.ts b/src/node/plugin.ts
index 8cd1eb4b..5ab7f459 100644
--- a/src/node/plugin.ts
+++ b/src/node/plugin.ts
@@ -79,7 +79,8 @@ export function createVitePressPlugin(
           if (req.url!.endsWith('.html')) {
             res.statusCode = 200
             res.end(
-              `<div id="app"></div>\n` +
+              `<!DOCTYPE html>\n` +
+                `<div id="app"></div>\n` +
                 `<script type="module" src="/@fs/${APP_PATH}/index.js"></script>`
             )
             return
