A seat trim assembly includes first and second seat trim members sized to be received upon a cross member of a seat back frame, and to each support a portion of a back of an occupant. The first seat trim member includes a first fastener arrangement. The second seat trim member includes a second fastener arrangement sized to engage the first fastener arrangement. The first fastener arrangement is oriented so that the first seat trim member can only be assembled to the cross member at an angle relative to the second seat trim member that is radially offset about the cross member from a fully assembled orientation.