P brought this action to recover three months' rent from Ds, who had vacated the leased home. Ds affirmatively alleged the house when leased was in a state of disrepair and violated the municipal housing code and that P violated his duty (upon renting the premises for occupancy by human beings) to repair promptly and correct all conditions which rendered the premises unsafe, unsanitary or otherwise untenantable. It was alleged that P was notified of these housing code violations in 1968. In June 1970 one tenant was struck by the falling bathroom ceiling, a city housing inspector then made up a notice of violations, the premises were declared to be a public nuisance, and Ds were ordered to vacate. Ds prayed P's petition be dismissed. A counterclaim, containing the same and additional allegations, demanded judgment for $1500 rent paid during the tenancy. The trial court dismissed the counterclaim because it failed to state any cause of action upon which relief could be granted. The court then held that Ds were estopped from complaining about the disrepair without moving or taking corrective action. The court directed a verdict to P and Ds appealed.