diff --git a/appengine/standard/firebase/firetactoe/templates/fire_index.html b/appengine/standard/firebase/firetactoe/templates/fire_index.html
index e6743bd5ecb..3b18380b533 100644
--- a/appengine/standard/firebase/firetactoe/templates/fire_index.html
+++ b/appengine/standard/firebase/firetactoe/templates/fire_index.html
@@ -1,5 +1,7 @@
+<!doctype html>
 <html>
   <head>
+    <meta charset="utf-8">
     {% include "_firebase_config.html" %}
     <link rel="stylesheet" type="text/css" href="static/main.css" />
     <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
