A safety belt system for a motor vehicle is provided. The safety belt system comprising a safety belt, a shoulder portion of the safety belt, a buckle element, a mobile region of the buckle element, which under the action of forces caused by a crash is mobile from an initial position in which the safety belt may slide along the buckle element into a final position, in which the safety belt is fixed to the buckle element. The safety belt cooperating with the mobile region, such that the mobile region is movable by a force acting on the shoulder portion which tensions the shoulder portion in the direction of extension of the belt, from its initial position into its final position. The fixing of the safety belt on the buckle element is carried out by the mobile region itself.