A medicament delivery device 10 comprising: a syringe receiving housing 12, having first and second casing parts 14,16 separably attachable to one another； a sleeve 24 receivable within housing 12 and comprising a tube having inner surface 28 and opposing outer surface 30； and a locking member 36 receivable within second casing 16, such that locking member 36 is axially movable between first and second axial positions relative to the second casing 16, where in the first axial position locking member 36 is engageable with the outer surface 30 to inhibit an axial movement of sleeve 24 relative to first casing 14 and in the second axial position locking member 36 is disengageable from outer surface 30. Locking member 36 may be moveable from the first axial position to the second axial position by separation of first and second casing parts 14,16 from one another. Locking member 26 may be engageable with outer surface 30, where locking member 26 comprises a body with radially inward protrusions 42 engageable with surface 30. Locking member 26 may be disengageable from outer surface 30 by a radially outward movement of the inward protrusions 42, which may be by deformation of locking member 26.
