A method for operating an electropneumatic parking brake system of a vehicle combination, which includes a tractor vehicle and a trailer vehicle, includes activating, after a parking operation and braking of the vehicle combination, a trailer check function in a standstill state. The trailer check function enables a check as to whether, in the case of a decrease in the braking action of the trailer vehicle, the vehicle combination can be held in a stationary manner solely by way of the braking action of a parking brake of the tractor vehicle. The trailer check function is carried out automatically when a vehicle combination has been braked in a stationary manner independently by way of an automatic parking function.