A device for an optical sensor for a motor vehicle and a corresponding driver-assistance system are disclosed. The optical sensor includes an optic. The device includes a housing that is mounted so as to be able to rotate around an axis of rotation and that has a compartment that is configured to accommodate the optical sensor, and an optical element that is securely fastened to the housing. The optical element has at least one planar surface that is configured to be placed in the field of view of the optical sensor. The device also includes and an actuator that is coupled to the housing in order to drive the housing and the optical element to rotate.