An active bolster for mounting at an interior trim surface of an automotive vehicle has a plastic-molded, expandable inner wall having a welding flange disposed at an outer perimeter and a pleated region bending inward from the welding flange. A plastic-molded outer wall overlies the inner wall, wherein the welding flange is hot welded to the outer wall to form an inflatable bladder for receiving an inflation gas. The inner wall further includes a blocking rib extending from between the welding flange and the pleated region into abutment with the outer wall to restrict flow of the inflation gas against the welding flange.