A seat for a vehicle includes a seat back and a seat bottom extending from the seat back along a seat-bottom axis. A track is fixed relative to the seat bottom and is elongated along the seat-bottom axis. A slider is slidably engaged with the track along the seat-bottom axis. A link is pivotally engaged with the slider. An armrest is pivotally engaged with the link. A pyrotechnic actuator connected to the slider. In the event of a sensed vehicle impact, the pyrotechnic actuator pulls the slider to move the armrest to a raised position.