An injection device includes an elongate housing (10), a syringe (12) disposed in the housing, and an internal piston (20) to express a dose from a needle (16) at its front end. The injection device further includes a shroud element (24) movable forwardly relative to the syringe to shroud the needle after use and a latch (74) movable between a latched state in which it restricts rearward movement of the shroud element, and a release state. The latch is moved to its latch state by a magnetic force (56).