Key legal question
Whether the appellate court violated federal law by upholding payment for extra works despite the contract's written-form requirement.
Extracted holding
No. The parties accepted the extra-work offers without reservation, which amounted to a subsequent waiver of the written-form requirement and made the new agreement binding.
Extracted reasoning
The Federal Court held that the appellate court had found a consensual agreement on the extra works. A prior contractual clause requiring written amendments does not prevent the parties from later waiving that form requirement by conclusive conduct; unreserved acceptance of the offers was sufficient.