Judgment unanimously affirmed, with costs. Memorandum: The trial court correctly concluded that the petition should be dismissed but we do not agree with the reasoning by which this result was reached. Petitioners sought a review of the board’s determination in this article 78 proceeding that granted Woman’s Club of Rochester a special permit to construct a club house in a residential district. The court proceeding was commenced by service of petition and notice on respondents on November 26,1968. The petition was noticed to be heard 13 days later on December 10. Respondents in their answer presented an affirmative defense that such service had not been made “at least twenty days before the time at which the petition (was) noticed to be heard” (CPLR 7804, subd. [c]). Petitioners thereafter moved to dismiss the affirmative defense and Special Term denied the motion. Thereafter, the trial court decided the issues presented upon the merits and dismissed the petition without passing on the preliminary question as to the timeliness of the service of petition and notice. This we conclude was error. The failure of petitioners to comply with the plain language of the statute was a jurisdictional defect. There is no evidence upon which to base a finding of a waiver by respondents of their right to assert and have decided this affirmative defense. Such a waiver could only be established by proof that respondents voluntarily relinquished a known right (Keller Tailors Trimmings Co. v. Burke Rugby, Inc., 308 N. Y. 441, 446). Dismissal of the petition is mandated on the ground that the court did not have jurisdiction of the proceeding and erroneously considered and decided the merits of the controversy (Matter of Beck v. Goodday, 24 A D 2d 1016; Matter of Tara Homes v. Volz, 44 Misc 2d 171). (Appeal from judgment of Monroe Special Term, dismissing petition.) Present — Goldman, P. J., Witmer, Moule, Bastow and Henry, JJ.