A method of operating a power-assisted hydraulic steering system of a motor vehicle having a hydraulic pump mechanically driven by a vehicle drive assembly, and having an additional function which reduces the amount of power assistance at a high driving speed in comparison to the assistance at a low driving speed and, in the process, simultaneously increases the quantity of hydraulic medium circulated by way of the hydraulic assistance unit of the steering gear is provided. This additional function is activated independently of the driving speed also under operating conditions which may subject the hydraulic pump to extreme stress. For example, the additional function may be activated shortly before reaching the steering end stop, which can be detected by use of an appropriately arranged steering angle sensor. An activation also is possible if steering angles which are larger than a defined limit steering angle are set for a defined time period. Furthermore, this additional function may be activated when the temperature of the hydraulic medium and/or the pressure on the pump delivery side exceed(s) a certain limit value(s), as required, also as a function of time.