Medicament delivery device comprising: - a housing (16, 18), arranged to accommodate a medicament container provided with a movable stopper; - a power unit arranged inside said housing, said power unit comprising a plunger rod, a drive spring arranged inside the plunger rod and operably arranged to act on the plunger rod and, which is, upon activation, operably arranged to act on said medicament container, an actuator comprising holding elements (94, 100), capable of releasibly holding said plunger rod with said drive spring in a tensioned state, and an actuator sleeve operably connected to said actuator for releasibly locking said holding elements (94, 100) in a holding state; said medicament delivery device further comprising: - a medicament delivery member guard slidably movable in said housing (16, 18) and arranged to act on said actuator sleeve for setting said holding elements (94, 100) with said actuator sleeve in a first activation state; - an activator unit arranged to be manually operated and which is operably arranged to act on a distal end of said plunger rod for setting said holding elements (94, 100) with said actuator sleeve in a second activation state, wherein said plunger rod is released when both activation states are set, characterised in an adjuster element (150, 178) operably arranged and positioned between said plunger rod and said activator unit, which adjuster element (150, 178) has a length that is chosen dependent on the initial position of the stopper in relation to the initial position of a proximal end of the plunger rod, wherein said adjuster element (150, 178) is arranged outside said drive spring as seen in a radial direction. - a housing (16, 18), arranged to accommodate a medicament container provided with a movable stopper; - a power unit arranged inside said housing, said power unit comprising a plunger rod, a drive spring arranged inside the plunger rod and operably arranged to act on the plunger rod and, which is, upon activation, operably arranged to act on said medicament container, an actuator comprising holding elements (94, 100), capable of releasibly holding said plunger rod with said drive spring in a tensioned state, and an actuator sleeve operably connected to said actuator for releasibly locking said holding elements (94, 100) in a holding state; said medicament delivery device further comprising: - a medicament delivery member guard slidably movable in said housing (16, 18) and arranged to act on said actuator sleeve for setting said holding elements (94, 100) with said actuator sleeve in a first activation state; - an activator unit arranged to be manually operated and which is operably arranged to act on a distal end of said plunger rod for setting said holding elements (94, 100) with said actuator sleeve in a second activation state, wherein said plunger rod is released when both activation states are set, characterised in an adjuster element (150, 178) operably arranged and positioned between said plunger rod and said activator unit, which adjuster element (150, 178) has a length that is chosen dependent on the initial position of the stopper in relation to the initial position of a proximal end of the plunger rod, wherein said adjuster element (150, 178) is arranged outside said drive spring as seen in a radial direction.