An assembly for a drug delivery device is provided, the assembly comprising a blocking element and a piston rod having an interaction feature which is adapted and arranged to mechanically cooperate with the blocking element. For delivering a dose of a drug, the piston rod is configured to be moved from an initial position to an end position with respect to the blocking element, wherein the interaction feature is provided along the path between the initial position and the end position. An operating noise is provided to the user when the interaction feature mechanically cooperates with the blocking element while moving the piston rod from the initial position to the end position for dose delivery. The interaction feature is adapted for homogenizing the operating noise so as to prevent the operating noise from being interpreted by the user as signalling the end of the dose delivery operation. Furthermore, a drug delivery device is provided.
