An exemplary airbag assembly includes an airbag and a duct having an duct opening for venting gas. The duct has a first position and a second position. The duct is configured to direct less gas out of the airbag when in the second position than when in the first position. A tether kinks about the duct to move the duct from the first position to the second position. The inflating causes the tether to kink about the duct.