In an airbag restraint system for automobile passenger safety, an airbag having a flexible fabric airbag wall defining an inflation chamber with a mouth in said airbag wall for communication of the closed inflation chamber with an inflator, has a portion of said airbag wall tucked inside the inflation chamber and held there by strips permanently attached to panels of the airbag wall parallel to fold lines on said panels where the tucked in portion of the airbag wall turns into the airbag. Those strips extend outward beyond said fold lines and are joined there by a weak seam that can be broken by tension in the airbag walls caused by inflation of the airbag to a desired inflation pressure. When the weak seam breaks, the strips are released and the tucked in portion of the airbag will be deployed and inflated to increase the volume capacity of the airbag and thereby decrease pressure in the airbag.