diff --git a/classes/Kohana/Model/Store/Purchase.php b/classes/Kohana/Model/Store/Purchase.php
index <HASH>..<HASH> 100644
--- a/classes/Kohana/Model/Store/Purchase.php
+++ b/classes/Kohana/Model/Store/Purchase.php
@@ -73,7 +73,7 @@ class Kohana_Model_Store_Purchase extends Jam_Model implements Purchasable {
 	{
 		if (($index = $this->search_same_item($new_item)) !== NULL)
 		{
-			$this->items[$index]->quantity += $new_item->quantity;
+			$this->items[$index]->quantity = $this->items[$index]->quantity + 1;
 		}
 		else
 		{
fix weird __set/__get bug with +=