‘No one can obtain an advantage by his own wrong.’ However, clause 20.1 of the FIDIC forms of contract appears to permit an employer to obtain an advantage where it has caused a delay and where the contractor has failed to give a notice in the 28 days specified. In such circumstance should a court or arbitrator uphold the notice provisions in the FIDIC contracts? This article considers what happens when a contractor fails to give a clause 20.1 notice with the result that the employer takes advantage of his or her own default. Under the FIDIC forms of contract, a contractor that wishes to make a claim for either time or additional money must give a notice in accordance with clause 20.1. Historically, courts and arbitrators in common law countries would hold the parties to their bargains whoever difficult or unconscionable the result might be. In recent years this position appears to be changing. The legislation in many common law countries imposes terms in contracts to protect consumers. In some jurisdictions, contacts may also be interpreted to avoid commercial absurdity, and in other jurisdictions the courts will strike down unconscionable bargains. There is also a doctrine, which is applied in many jurisdictions, that ‘No one can obtain an advantage by his own wrong’ (De Zotell v Mutual Life Ins. Co. of New York, 60 SD 532, 245. NW 58, 59). It is sometimes described as a ‘principle of equity’ and expressed in the maxims: ‘ex injuria non oritur jus’ or ‘the clean hands theory’.