A restraint system includes a housing defining a cavity tapering to an end and a plug disposed in the cavity. The plug is larger than the end of the housing. A seatbelt buckle is fixed relative to one of the housing and the plug and is moveable from a first position to a second position relative to the other of the housing and the plug. The plug is moveable relative to the housing toward the end during movement from the first position to the second position. One of the housing and the plug is plastically deformable by the other of the housing and the plug during movement from the first position to the second position.