Hydraulic circuit, in particular for a steering system of a multi-axle vehicle, comprising a hydraulic cylinder which includes a cylinder chamber , a piston sealingly mounted in the cylinder chamber and dividing the cylinder chamber into two working chambers , and at least one piston rod carried by the piston , a mechanically switchable valve arrangement with at least three switching positions, and a mechanical probe element , which interacts with the piston or the piston rod and is configured to switch the valve arrangement between the three switching positions depending on the deflection of the piston , wherein the valve arrangement is configured, in a first switching position, to connect a first of the working chambers to a tank return line (T) or to establish a unidirectional hydraulic connection from the first to the second working chamber to enable a return movement of the piston into a safe fail position; in a second switching position, which corresponds to the safe fail position of the piston , to block the connection between the working chambers or to the tank return line (T); and in a third switching position, to connect the second working chamber to the tank return line (T) or to an additional tank return line, or to establish a unidirectional hydraulic connection from the second to the first working chamber , to enable an opposite return movement of the piston into the safe fail position, characterized in that the valve arrangement includes a fourth switching position in which the connection between the working chambers or to the tank return line (T) is blocked, and the hydraulic circuit comprises an actuator separate from the hydraulic cylinder , in particular a hydraulic actuator (22; 22), which is configured, when actuated, to disengage the probe element from interaction with the piston or the piston rod , and to switch the valve arrangement into the fourth switching position. a hydraulic cylinder which includes a cylinder chamber , a piston sealingly mounted in the cylinder chamber and dividing the cylinder chamber into two working chambers , and at least one piston rod carried by the piston , a mechanically switchable valve arrangement with at least three switching positions, and a mechanical probe element , which interacts with the piston or the piston rod and is configured to switch the valve arrangement between the three switching positions depending on the deflection of the piston , wherein the valve arrangement is configured, in a first switching position, to connect a first of the working chambers to a tank return line (T) or to establish a unidirectional hydraulic connection from the first to the second working chamber to enable a return movement of the piston into a safe fail position; in a second switching position, which corresponds to the safe fail position of the piston , to block the connection between the working chambers or to the tank return line (T); and in a third switching position, to connect the second working chamber to the tank return line (T) or to an additional tank return line, or to establish a unidirectional hydraulic connection from the second to the first working chamber , to enable an opposite return movement of the piston into the safe fail position, characterized in that the valve arrangement includes a fourth switching position in which the connection between the working chambers or to the tank return line (T) is blocked, and the hydraulic circuit comprises an actuator separate from the hydraulic cylinder , in particular a hydraulic actuator (22; 22), which is configured, when actuated, to disengage the probe element from interaction with the piston or the piston rod , and to switch the valve arrangement into the fourth switching position. <EOS>