This passive safety device (1) comprises an inner needle shield (4) having a proximal end (40) configured to be sealed to a tip (102) of an injection device (100), a distal portion (42) configured to be pricked by a needle (108) in a pre-use position and pierced by the needle (108) in an injection position, and an energy storage portion (44) configured to accumulate energy as the passive safety device (1) passes from the pre-use position to the injection position and release energy as the passive safety device (1) passes from the injection position to a safety position. The passive safety device (1) further comprises a sleeve (2) surrounding the proximal end (40), an outer needle shield (6) having a proximal end (62) slidably attached to the sleeve (2) so that the outer needle shield (6) is movable relative to the sleeve (2), and a lock configured to lock the outer needle shield (6) in the safety position. The inner needle shield (4) is configured to move the outer needle shield (6) distally as the energy storage portion (44) releases its stored energy.
