A method for ensuring a braking effect utilizes a service brake system and a parking brake system of a vehicle. The service brake system is configured to be actuated irrespective of a driver input, and the parking brake system is activated by an extraneous force, for example in an electromechanical arrangement. When a deceleration request is received, the service brake system is initially actuated. If a deceleration variable remains below a target value and the measured slip is smaller than a slip threshold value, the parking brake system is actuated in order to bring the vehicle to a standstill.