The invention relates to a protection device (10) for a needle of an assembly or of an injection device having a hub portion provided with a needle, the said protection device (10) comprising: an outer casing (20) formed of a first material； and an inner casing (30) formed of a second material different from the said first material and defining a cavity (32) for receiving in a sealing way at least the hub portion, said cavity (32) having an inner wall (34)； attachment means (40) defined in the said cavity (32) to removably engage and secure said protection device (10) at least along a sealing line to the injection device； the protection device being characterized in that it further comprises aspiration limiting means (40, 50) for limiting the deformation of said cavity (32) when said protection device (10) is separated from the assembly or the injection device.
