diff --git a/src/web/app/boot.js b/src/web/app/boot.js
index c5dc6845af..ab147eb562 100644
--- a/src/web/app/boot.js
+++ b/src/web/app/boot.js
@@ -15,6 +15,8 @@ require('./common/tags');
  * MISSKEY ENTORY POINT!
  */
 
+"use strict";
+
 document.domain = CONFIG.host;
 
 // Set global configration