A securing device for an injection device which receives a syringe with a proximal end portion having a radially outwardly projecting flange, has a body with proximal and distal end portions, an opening for accepting the syringe, an outer surface, and a proximal end surface for contacting a distally-facing surface of the flange when the syringe is advanced distally, preventing further advancement. A securing arm includes a free end； a base end fixed to the outer surface； a first portion extending radially outwardly from the base end to permit the flange to pass； and a second portion extending radially inwardly in a rest position, contacting the flange as the syringe is advanced. The securing arm is elastically flexible to allow the free end to move radially outwardly, allowing the advancing flange to pass, and is biased to the rest position to secure the flange and the syringe against proximal movement.
