Article 37 CISG
If the seller has delivered goods before the date for delivery, he may, up to that date, deliver any missing part or make up any deficiency in the quantity of the goods delivered, or deliver goods in replacement of any non-conforming goods delivered or remedy any lack of conformity in the goods delivered, provided that 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.