[TYPO3-shop] problem with stock management

[Aurélien]

Hello,

I've got a problem to manage my stock (excuse my bad english). When I order
some products, the number in stock doesn't reduce. I've set alwaysInStock to
0. In, the file class.tx_ttproducts_order.php, I see these lines
if (!$this->conf['alwaysInStock'] && !$this->conf['AlwaysInStock']) {

$rc = $tt_products->reduceInStock($this->basket->itemArray,
$this->conf['useArticles']);

}

 so I had in my template typo3
plugin.tt_products.alwaysInStock = 0
plugin.tt_products.AlwaysInStock = 0
but it doesn't change anything.

If I order more that I've in stock, there is no error message ...
I don't understand wht's wrong

I use tt_products 2.4.9 and typo3 3.8.1

Thanks.
Aurélien