Article 36 CISG
(1) The seller is liable in accordance with the contract and this Convention for any lack of conformity which exists at the time when the risk passes to the buyer, even though the lack of conformity becomes apparent only after that time.
(2) The seller is also liable for any lack of conformity which occurs after the time indicated in the preceding paragraph and which is due to a breach of any of his obligations, including a breach of any guarantee that for a period of time the goods will remain fit for their ordinary purpose or for some particular purpose or will retain specified qualities or characteristics.