diff --git a/src/CartItemOptions.php b/src/CartItemOptions.php
index 1998e69..fd924dc 100644
--- a/src/CartItemOptions.php
+++ b/src/CartItemOptions.php
@@ -9,11 +9,9 @@ class CartItemOptions extends Collection
     /**
      * Get the option by the given key.
      *
-     * @param string $key
-     *
      * @return mixed
      */
-    public function __get($key)
+    public function __get(string $key)
     {
         return $this->get($key);
     }