diff --git a/src/Lists/AbstractItemList.php b/src/Lists/AbstractItemList.php
index 5778071..866629e 100644
--- a/src/Lists/AbstractItemList.php
+++ b/src/Lists/AbstractItemList.php
@@ -62,7 +62,7 @@ public function getAll()
      *
      * @return  SimpleIndexIterator
      */
-    public function getIterator()
+    public function getIterator(): \Traversable
     {
         return new SimpleIndexIterator($this->getAll());
     }