A self-adjustable anti-chucking device for a vehicle liftgate includes a wedge portion that is attachable to the liftgate and a base portion that is attachable to a vehicle body. The wedge portion includes a wedge-shaped slider block that is biased by a resilient member. The base portion includes an oblique surface shaped to contact a surface of the slider block. When the liftgate is closed and latched, the friction between the slider block and the oblique surface and the biasing force of the resilient member securely hold the liftgate in place. If the liftgate shifts position, the biasing force of the resilient member will cause the slider block to shift to compensate for any change in the liftgate position relative to the vehicle body.