Provided is a medicament delivery device (100) that is reliable, safe and intuitive to use and at the same time is easy to use when handling. This is achieved by a medicament delivery device (100) comprising a tubular housing (120, 130) having a proximal end (308) and an opposite distal end (309), an actuator member (110) being coaxially arranged at the distal end (309) of the tubular housing (120, 130) and movably arranged, in relation to the tubular housing (120, 130) and a cap (140) being releasably connected to the proximal end (308) of the tubular housing (120, 130) wherein the medicament device (100) further comprises a longitudinal actuator interlocking member (150) movably arranged within the tubular housing (120, 130) and interactively connected to both the actuator member (110) and to the cap (140) for controlling movement of the actuator member (110). Thus the cap (140) acts as a device enabler, i.e. it is impossible to actuate the medicament delivery device (100) until the cap (140) has been removed.