diff --git a/src/Gloudemans/Shoppingcart/Cart.php b/src/Gloudemans/Shoppingcart/Cart.php
index 88cd147..16c437a 100644
--- a/src/Gloudemans/Shoppingcart/Cart.php
+++ b/src/Gloudemans/Shoppingcart/Cart.php
@@ -231,7 +231,7 @@ class Cart {
      */
     protected function generateRowId($id, $options)
     {
-        return md5($id . serialize($options));
+        return md5($id . serialize(ksort($options)));
     }
 
     /**