An occupant restraint system of a vehicle includes a roof rail airbag that is located at a roof rail of the vehicle and above a door of the vehicle and that is configured to deploy in an outboard direction. A deployment device, when triggered, deploys the roof rail airbag. An actuator, when triggered, actuates a deployable reaction surface (i) from a first state where the deployable reaction surface is stowed behind interior door trim and does not block any part of a window opening of the door when viewed from inboard of the deployable reaction surface (ii) to a second state where the deployable reaction surface blocks at least a portion of the window opening of the door when viewed from inboard of the deployable reaction surface.