Section 12 of the Matrimonial Causes Act 1973 as amended by the Gender Recognition Act 2004 requires transgender people to disclose their ‘gender history’ to the other party to a marriage prior to the marriage ceremony. Failure to do so enables the other party to exit the relationship through nullity proceedings. This article argues that this provision is discriminatory and encroaches on the right to privacy, breaching Articles 14 and 8 of the European Convention on Human Rights. It challenges the idea, implicit in the provision, that non-disclosure of gender history is unethical or fraudulent. Crucially, the article considers and rejects the claim that discrimination against and encroachments on the privacy of transgender people are justified because inadvertent sexual congress with a transgender person is potentially harmful. Finally, if a consent-based right to know exists, it argues that it ought to be trumped by considerations of justice, legal consistency and public policy.