In what can only be described as an extreme case of mistaken identity, a Belgian man wants his marriage annulled after finding out his wife of 19 years used to be a man.

The man, identified only as "Jan," married his wife Monica in 1993, The Telegraph reported.

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He told the Het Nieuwsblad newspaper that they decided against children, since he already had two from a previous marriage, and that his wife tricked him into thinking she menstruated by using sanitary towels "to conceal the truth."

"Even during sex, I never noticed anything," Jan said.

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He discovered the truth after rumors began circulating that Monica had once been a man.

"I pushed her against the wall and said, 'Now I know the truth. Are you a man?' She then announced that she was born as a boy and that she had been operated on. … My world collapsed," Jan told Het Nieuwsblad.

Currently undergoing psychiatric treatment, Jan has started legal proceedings to have the marriage annulled, The Daily Mail reported.