An injection device and an injection device trainer for training a user to use an injection device. Each one of the injection device and the injection device trainer can include: a body portion； and an actuator positioned towards a proximal end of the body portion, the actuator moveable from a proximal position to a distal position； wherein the body portion comprises a body protrusion and the actuator comprises a latch that is arranged to couple with the body protrusion when the actuator is in the distal position, thus holding the actuator in the distal position.
