The invention relates to an adaptor (10) for the distal tip (2) of a drug delivery device, comprising : - an inner ring (20) comprising retaining means capable of exerting a radial inward force on said distal tip and of switching from a free configuration to a locked configuration, in which the radial inward force they exert on said conical distal tip limits the axial movement of the adaptor, - compressing means (30) movable axially with respect to said retaining means between a proximal position, in which said compressing means do not exert a centripetal pressure on said retaining means, and a distal position, in which they exert a centripetal pressure on said retaining means. The invention further relates to a drug delivery device comprising such an adaptor and to a method for mounting said adaptor on said drug delivery device.
