diff --git a/Code/Module/Manifest.php b/Code/Module/Manifest.php
index 9d69c01d2..3558e1d49 100644
--- a/Code/Module/Manifest.php
+++ b/Code/Module/Manifest.php
@@ -10,6 +10,9 @@ class Manifest extends Controller
 
     public function init()
     {
+        if ($_REQUEST['module_format'] !== 'webmanifest') {
+            http_status_exit(418, "I'm a teapot");
+        }
         $ret = [
             'name' => System::get_project_name(),
             'short_name' => System::get_project_name(),