The invention relates to an injection device for self-administration of doses of a liquid drug. The injection device carries a needle cannula (15) which is concealed by a telescopically movable shield (20). Further a stopping means (30) interconnects the shield with the helical rotatable scale sleeve (25) such that the shield can only be operated proximally when the scale sleeve is rotated away from its zero position. Once the scale sleeve returns to its zero position during expelling of the dose, the shield and the stopping means is allowed to slide distally and thus return to the locked position.