A material handling machine can be operated in a bucket shake control mode to override proportional control of a valve controlling fluid flow to and from a bucket tilt cylinder of the machine. Fluid flow through the valve upon actuation of a tilt controller such a joystick therefore is proportional to actuator stroke when the shake control system is deactivated and is always maximized regardless of actuator stroke when the shake control system is activated. Bucket shake control is activated through the manual operation of a control device such as a joystick-mounted switch. As a result of this arrangement, proportional control valve actuation always occurs immediately upon bucket tilt controller movement in a direction that is dependent upon a direction of bucket tilt controller movement from the neutral position thereof.