diff --git a/http_cache.rst b/http_cache.rst
index 458839c371e..5dbe30c7f8f 100644
--- a/http_cache.rst
+++ b/http_cache.rst
@@ -215,7 +215,7 @@ The *easiest* way to cache a response is by caching it for a specific amount of
     use Symfony\Component\HttpFoundation\Response;
     // ...
 
-    public function index()
+    public function index(): Response
     {
         // somehow create a Response object, like by rendering a template
         $response = $this->render('blog/index.html.twig', []);