An active bolster mounts at an interior trim surface of a passenger compartment in an automotive vehicle. A plastic-molded, expandable front wall deploys toward a passenger in the passenger compartment. A plastic-molded back wall is joined around a substantially sealed perimeter with the front wall to form an inflatable bladder. The back wall includes an inflator receptacle defined by a raised recess wall having an inflator aperture. An inflator with a gas outlet end and an electrical connector end is received in the inflator aperture with the gas outlet end inside the inflatable bladder. The recess wall has a predetermined thickness for substantially retaining shape during inflation of the bladder. The inflator receptacle includes a flexible seal disposed around an inner edge of the inflator aperture comprised of a flashing edge bearing against the inflator and having a thickness less than the predetermined thickness of the recess wall.