diff --git a/src/dev.html b/src/dev.html
index d68d8591..2c641d13 100644
--- a/src/dev.html
+++ b/src/dev.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="zh-Hant-TW">
   <head>
     <title><%= process.env.PTTCHROME_PAGE_TITLE %></title>
     <link rel="icon" type="image/png" href="<%= require('./icon/logo.png') %>">
