Order, Supreme Court, New York County (Herman Cahn, J.), entered on or about December 17, 1996, which denied defendant’s motion for summary judgment on the issue of damages under its counterclaim, and granted plaintiff leave to amend its pleading to include an affirmative defense to defendant’s counterclaim alleging defendant’s failure to mitigate its damages, unanimously affirmed, without costs.
Issues of fact exist as to whether defendant acted reasonably to mitigate its damages, including when defendant first became aware of plaintiffs nonperformance of the contract, and, once aware, whether its method of mitigation was reasonable (see, Bernstein v Freudman, 180 AD2d 420). Defendant does not demonstrate or even allege prejudice or surprise by the requested amendment (CPLR 3025 [b]; Fahey v County of Ontario, 44 NY2d 934), and it is of no consequence that plaintiff raised the unpleaded defense for the first time to defeat summary judgment (see, Denburg v Parker Chapin Flattau & Klimpl, 213 AD2d 297; Siegel, Practice Commentaries, Mc*481Kinney’s Cons Laws of NY, Book 7B, CPLR C3212:10, at 318). Concur—Sullivan J. P., Ellerin, Nardelli, Williams and Andrias, JJ.