diff --git a/core/includes/bootstrap.inc b/core/includes/bootstrap.inc
index e7da6ec..369d15a 100644
--- a/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -2598,7 +2598,7 @@ function drupal_fast_404() {
     $fast_paths = variable_get('404_fast_paths', FALSE);
     if ($fast_paths && preg_match($fast_paths, request_path())) {
       drupal_add_http_header('Status', '404 Not Found');
-      $fast_404_html = variable_get('404_fast_html', '<html xmlns="http://www.w3.org/1999/xhtml"><head><title>404 Not Found</title></head><body><h1>Not Found</h1><p>The requested URL "@path" was not found on this server.</p></body></html>');
+      $fast_404_html = variable_get('404_fast_html', '<!DOCTYPE html><head><title>404 Not Found</title></head><body><h1>Not Found</h1><p>The requested URL "@path" was not found on this server.</p></body></html>');
       // Replace @path in the variable with the page path.
       print strtr($fast_404_html, array('@path' => check_plain(request_uri())));
       exit;
