diff --git a/src/Symfony/Component/HttpFoundation/HeaderBag.php b/src/Symfony/Component/HttpFoundation/HeaderBag.php
index 4683a684095a5..d7c46d377b8bf 100644
--- a/src/Symfony/Component/HttpFoundation/HeaderBag.php
+++ b/src/Symfony/Component/HttpFoundation/HeaderBag.php
@@ -65,7 +65,7 @@ public function __toString()
      *
      * @param string|null $key The name of the headers to return or null to get them all
      *
-     * @return array<string, array<int, string|null>>|array<int, string|null>
+     * @return ($key is null ? array<string, array<int, string|null>> : array<int, string|null>)
      */
     public function all(string $key = null)
     {