The motion court improvidently exercised its discretion by denying defendant's well-grounded motion to vacate its default pursuant to CPLR 5015 (a) (1) ( see Goldman v. Cotter, 10 AD3d 289). Defendant demonstrated a reasonable excuse for the default, entered by the court sua sponte on the one occasion that defendant failed to appear, with candid, detailed and uncontroverted allegations of law office failure. The four-month delay in seeking vacatur was well within the statutory time limit and was not unreasonable, given defendant's demonstrated intention to pursue the litigation, which had reached the stage of jury selection, and the absence of willful delay or a pattern of neglect either pre or postdefault. The prejudice alleged by plaintiff was mere conclusory conjecture, since no supporting evidence was submitted on this issue and the witness in question was apparently available ( see Werner v. Tiffany Co., 291 AD2d 305). Defendant also made the requisite prima facie showing of a meritorious defense to plaintiff's account stated claim, by specifying instances where plaintiff's performance of work was allegedly unauthorized or poorly performed resulting in defendant suffering damages ( see Tat Sang Kwong v Budge-Wood Laundry Serv., 97 AD2d 691).