Article 50
If the goods do not conform with the contract and whether or not the price has already been paid, the buyer may reduce the price in the same proportion as the value that the goods actually delivered had at the time of the delivery bears to the value that conforming goods would have had at that time. However, if the seller remedies any failure to perform his obligations in accordance with article 37 or article 48 or if the buyer refuses to accept performance by the seller in accordance with those Articles, the buyer may not reduce the price.