A materials handling vehicle is provided comprising: a base; a carriage assembly movable relative to the base; at least one cylinder coupled to the base to effect movement of the carriage assembly relative to the base; and a hydraulic system to supply a pressurized fluid to the cylinder. The hydraulic system includes an electronically controlled valve coupled to the cylinder. The vehicle further comprises control structure to control the operation of the valve such that the valve is closed in the event of an unintended descent of a carriage assembly in excess of a commanded speed.