A system includes a base. The system includes a buckle movable from a retracted position away from the base to an extended position. The system includes an actuator supported by the base and operatively coupled to the buckle to move the buckle to the extended position. The system includes a computer having a processor and a memory storing instructions executable by the processor to actuate the actuator to move the buckle to the extended position in response to determining that tension of a seatbelt webbing is above a predetermined threshold and that a vehicle impact has not been detected.