On 3 January 2017 the Court of Appeal in Amsterdam confirmed that a public contract that is rightfully concluded after the decision in first instance, can only be challenged in very strict circumstances. One of those circumstances is nullity of the contract based on Article 3:40 of the Dutch Civil Code. In this case, the claimant stated that the structure of the tender procedure infringed competition law and should therefore result in nullity of the contract that was awarded as a result of that tender procedure to another tenderer. Although the Court of Appeal agrees that infringement of Article 6 of the Dutch Competition Law or Article 101 TFEU would result in such nullity, it holds that this infringement was insufficiently proven by the claimant. With regard to competition law infringements, a great burden of proof lies with the claimant: he has to substantiate his claim with (economical) facts and circumstances. Brief statements regarding the relevant market and supposed market shares do not suffice.