Abstract: An optical sensor for detecting wetting of a surface in a motor vehicle, the optical sensor has a measuring segment which has at least one transmitter of electromagnet waves and at least one receiver of electromagnetic waves and in which a windshield is disposable so that when a layer of moisture forms on the windshield upon wetting from precipitation a wave propagation between the at least one transmitter and the at least one receiver changes and an output signal generated by the receiver changes, a housing disposable on an inside of the windshield and having a bottom face adapted to be in physical contact with the windshield, the bottom face of the housing being oval.