The invention relates to a protective circuit for a CAN-bus transceiver that is designed voltagewise for a first vehicle electric system, said transceiver being operated in a second vehicle electric system with a voltage that is several times higher than the voltage of the first vehicle electric system, comprising two diodes arranged between the bus terminal leads of the transceivers whose cathodes are connected to one another and to which a predetermined potential is applied, in addition to a limiting resistor mounted between each of the bus terminal leads of the transceiver and the bus line assigned thereto and two current mirror circuits for maintaining the require voltage level in the bus lines.