Article 39 - Loss of right to avoid

(1) If a party is entitled to avoid the contract for mistake but the other party declares itself willing to perform or performs the contract as it was understood by the first party, the contract is considered to have been concluded as the first party understood it. The second party must make such a declaration or render such performance promptly after having been informed of the manner in which the first party had understood the contract and before the first party has acted in reliance on a notice of avoidance.
(2) After such a declaration or performance the right to avoidance is lost and any earlier notice of avoidance is ineffective.