Action to recover damages for personal injuries sustained when plaintiff fell down a stairway in a building owned by his employer, through the alleged negligence of defendants, the general contractor and a subcontractor, engaged in construction work therein. Plaintiff appeals from a judgment entered on the verdict of a jury in favor of defendants. Judgment unanimously affirmed, without costs. In our opinion, the references to workmen’s compensation were unnecessary and improper but were waived by plaintiff by cross-examination of an officer of his employer with respect thereto and by calling a witness from the compensation carrier. (Johnson v. Gianino, 279 App. Div. 760.) It was error to refuse to charge, at plaintiff’s request, that if two causes contribute to an accident and if defendant was responsible for only one of these causes, the defendant is nevertheless liable for the full consequences of the accident. However, on this record, the error was not prejudicial. Present ■—• Nolan, P. J., Wenzel, Beldock, Murphy and Ughetta, JJ.