The present invention relates to injection devices for injecting a dose of a medicament. The injection device (100) incorporates a housing (101), a needle assembly (150) and a cover (200). The needle assembly (150) comprises an injection needle (152,153) accommodated in a needle container (151) having an opening which in a storage state of the injection device (100) is sealed by a film seal (155). The cover may include sections (201,202) arranged movable relative to the housing (101). The injection device (100) is so configured that upon movement of the cover sections (201,202) relative to the housing (101) the film seal (155) is changed from a sealing state to an unsealing state for shifting the injection device (100) into a ready-to-administer state.