—Order, Supreme Court, New York County (Edward Lehner, J.), entered April 5, 2000, which denied defendant’s motion to vacate a prior order, entered September 13, 1999, granting plaintiffs motion to strike defendant’s answer on default, unanimously reversed, on the law, the facts, and in the exercise of discretion, without costs, the motion to vacate granted, and the answer reinstated.
The motion court improvidently exercised its discretion in denying defendant’s motion to vacate the default order. Defendant established, as required by CPLR 5015, a reasonable excuse for the default, i.e., inadvertent law office failure, and a meritorious defense. As to the latter issue, the affirmation submitted by defendant’s attorney, whether or not based on his personal knowledge of the underlying facts, was a proper vehicle for the submission of evidence in admissible form (see, Grossberg Tudanger Adv. v Weinreb, 177 AD2d 377, 378; Zuckerman v City of New York, 49 NY2d 557, 563), consisting of agreement between defendants and a waste disposal contractor purporting to show that maintenance of the waste compactor unit that was the alleged cause of plaintiffs slip and fall injury was the responsibility of the contractor. Concur — Rosenberger, J. P., Williams, Wallach, Saxe and Buckley, JJ.