A farm implement has a frame that is foldable between an extended, working position and a folded, for-transport position has a hydraulic system that controls the flow of hydraulic fluid to a series of actuators that raise and lower the implement. The hydraulic system is controlled by a control lever or arm that rotates a rockshaft to open and close hydraulic valves to change the flow of hydraulic fluid to the actuators. To prevent the unintentional lowering of the implement frame when the implement is in transport, a lockout arrangement engages the rockshaft to prevent rotation of the rockshaft when the frame is in the folded position. The lockout arrangement locks out the rockshaft automatically when the frame is raised to the folded position.