An apparatus (10) for helping to protect an occupant of a vehicle includes an inflatable vehicle occupant protection device (12). An inflator (14) provides inflation fluid for inflating the protection device (12). A vent member (30) includes at least one vent opening (62) for venting the inflation fluid. A vent cover (100) has a closed condition for blocking fluid flow through the at least one vent opening (62) and an open condition for permitting fluid flow through the at least one vent opening. The vent cover (100) includes a side wall (110) that has at least one portion (134, 372) that projects from the side wall into the vent member (30) to help maintain the vent cover in the closed condition.