Disclosed is a brake system of the ‘brake-by-wire’ type for actuating a motor vehicle brake system having a brake booster which is operable in response to the driver's input by a brake pedal and to an electronic regulating and control unit. A device is provided to decouple a force-transmitting connection between the brake pedal and the brake booster in the ‘brake-by-wire’ operating mode. The electronic regulating and control unit (7) includes a control circuit for controlling the travel (SDs) covered by the output member (20) of the brake booster (3), the nominal value (SDsnominal) of the travel (SDs) covered by the output member (20) of the brake booster (3) is calculated corresponding to the actuating travel (SBp) of the brake pedal (1), and a monitoring module (24) is provided which, in the case of a fault such as the inclusion of air or brake circuit failure, performs a partial compensation of the extension of the travel (SDs) covered by the output member (20) of the brake booster (3), which extension is caused by the fault.