A wheelchair lift for mounting to a vehicle includes a platform assembly configured to support a wheelchair. The wheelchair lift includes a roll stop to be moved between an entry position to allow a wheelchair to be loaded to or unloaded from the platform assembly, and a barrier position to prevent the wheelchair from falling off the platform assembly. The wheelchair lift includes a mechanical actuator mechanism for moving the roll stop between the entry position and the barrier position. The mechanical actuator mechanism is configured to keep the roll stop in the entry position, when the platform assembly is in a ground level position, and to block the roll stop from moving from the barrier position to the entry level position, when the platform assembly is in the horizontal position.