A medicament delivery device including a first container having a delivery outlet at a front end thereof and a first stopper axially moveable in the first container, the first stopper defining and separating a first chamber and a second chamber in the first container, where the first chamber is axially forwards of the first stopper and the second chamber is axially rearwards of the first stopper. The medicament delivery device further includes a second container having a second stopper axially moveable in the second container, the second stopper defining and separating a third chamber and a fourth chamber in the second container, where the third chamber is axially forwards of the second stopper and the fourth chamber is axially rearwards of the second stopper, and where the third chamber has a vent outlet in fluid communication with a venting chamber.