The invention relates to a device (101) for altering the control times of gas exchange valves of an internal combustion engine, having a hydraulic actuating device (102) and a control valve (103). The device (101) according to the invention is provided with centre-position locking of a hydraulic actuating device (102). Furthermore, the device (101) according to the invention ensures that if an actuating unit (112) which governs the control valve (103) fails, the hydraulic actuating device (102) is locked in the central position and the locking is maintained until the actuating unit (112) is repaired. Furthermore, the device (101) according to the invention allows the internal combustion engine to be started in a locked position in a central position without a moveable element (105) of the hydraulic actuating device (102) striking a side wall of a pressure space (104) when the internal combustion engine is started.