Article 34 CISG
If the seller is bound to hand over documents relating to the goods, he must hand them over at the time and place and in the form required by the contract. If the seller has handed over documents before that time, he may, up to that time, cure any lack of conformity in the documents, if the exercise of this right does not cause the buyer unreasonable inconvenience or unreasonable expense. However, the buyer retains any right to claim damages as provided for in this Convention.