The present invention relates to a drug delivery device for dispensing of a dose of a medicament, the device comprising: an elongated housing extending in an axial direction to accommodate a cartridge containing a medicament to be dispensed, wherein the housing being further adapted to detachably support a needle assembly at a distal end thereof, a drive mechanism comprising a piston rod to operably engage with a piston of the cartridge, a protecting sleeve slidably attached to the distal end of the housing to enclose the needle assembly in a distal stop position and to expose the needle assembly in a retracted proximal stop position, and an interlocking member operably engaged with the protecting sleeve and being axially displaceable relative to the housing between a locking position, in which the protecting sleeve is locked to the housing, and a release position, in which the protecting sleeve is axially displaceable relative to the housing.
