diff --git a/system/Cookie/CookieStore.php b/system/Cookie/CookieStore.php
index 8ef45c970f59..87dc472d1fe5 100644
--- a/system/Cookie/CookieStore.php
+++ b/system/Cookie/CookieStore.php
@@ -207,7 +207,7 @@ public function count(): int
      *
      * @return Traversable<string, Cookie>
      */
-    public function getIterator()
+    public function getIterator(): Traversable
     {
         return new ArrayIterator($this->cookies);
     }