Inhaler device (10) comprising an actuator body (20) and an inhaler canister assembly (70), the inhaler canister assembly (70) is comprised of a canister (30) with a metering valve at a valve end and a dose counter unit (60) attached to a base end thereof. Further, the inhaler canister assembly (70) comprises first position ensuring means (110, 230), the actuator body comprises second position ensuring means (120,210), wherein the first and second position ensuring means being complementary mating means, and the first and second position ensuring means being so arranged that the inhaler device (10) cannot be fired, nor the counter unit (60) count unless the first and second position ensuring means are in a mating relationship. There is also provided an inhaler canister assembly (70) and an actuator body (20).