A head brace and a method for attaching a stub sill to a tank of a railroad tank car by the use of such a head brace. A stub sill includes side plates having ears that extend upward to support the tank near where the head of the tank is attached, and a head brace is welded to the side plates and to the head of the tank in a weld joint that can be continuous along the head brace from the ears of the side plate to the center of the head brace. Doublers may be provided on the sill where the head brace is welded to the side plates.