In order to prevent the unloader from rotating relative to the valve seat, it is proposed to design the anti-rotation lock for the unloader as an anti-rotation locking disk (16) on which a central recess (17) is provided which has a cross-section that is diametrically opposed and matched to the valve nut (10), wherein the anti-rotation locking disk (16) is arranged with its central recess (17) in a non-rotational manner on the valve nut (10), and the outer contour of the anti-rotation locking disk (16) has a non-circular cross-section, and a central recess (24) is provided on the unloader (20), said central recess having an inner contour diametrically opposed and matched to the outer contour, and the unloader (20) is arranged with its central recess (24) on the anti-rotation locking disk (16).