diff --git a/public/index.php b/public/index.php
index 5171431e..0085336d 100644
--- a/public/index.php
+++ b/public/index.php
@@ -17,7 +17,7 @@ ob_start();
 if(is_file($msz->dbCtx->getMigrateLockPath())) {
     http_response_code(503);
     header('Content-Type: text/html; charset=utf-8');
-    header('X-Accel-Redirect: /error-503.html');
+    echo file_get_contents(sprintf('%s/error-503.html', Misuzu::PATH_PUBLIC));
     exit;
 }