A robotic carton unloader for unloading cartons in a carton pile has a mobile body and a movable robotic arm attached to the mobile body that has an end effector at a movable end thereof to unload cartons from the carton pile. A conveyor system is attached to the mobile body and extends from front to rear of the carton unloader to convey cartons received thereon by the moveable robotic arm. The conveyor system comprises a central portion carried on the mobile body and a front portion extending therefrom towards the carton pile. The front portion is configured to change width from narrow to wider to act as a shield to catch and then move falling cartons received thereon.