The present invention relates to a drug delivery device (100) comprising : - a reservoir (10) for a product, having a distally projecting end-piece (20) defining an axial passageway for the transfer of the product, with a distal portion (23), - an adaptor (30) having a collar (31) engageable around said end-piece said collar being axially movable with respect to said end-piece, - securing means (13, 24, 32) for limiting the axial movement of said collar with respect to said end-piece, between a most distal position and a most proximal position of said collar, biasing means (34 39 62 70) for urging said collar towards its most distal position. The invention also relates to such an adaptor.
