diff --git a/templates/errors/400_http.erb b/templates/errors/400_http.erb
index 6bc1df2..374a1d5 100644
--- a/templates/errors/400_http.erb
+++ b/templates/errors/400_http.erb
@@ -4,7 +4,11 @@ Connection: close
 Content-Type: text/html
 
 <!DOCTYPE html>
-<html><body><h1>400 Bad request</h1>
+<html lang="en">
+<head>
+  <title>400 Bad request</title>
+</head>
+<body><h1>400 Bad request</h1>
 Your browser sent an invalid request.
 </body></html>
 
