An assembly for a drug delivery device comprises a drive member which is adapted and arranged to be displaced in a dose setting direction for setting a dose of a drug and to be displaced in a dose delivery direction for delivering the set dose of the drug. The assembly comprises a piston rod which is adapted and arranged to be displaced in the dose delivery direction via mechanical interaction with the drive member for delivering the set dose. The assembly comprises at least one resilient pre-delivery element, wherein the assembly is configured such that the resilient pre-delivery element is biased when the drive member is displaced in the dose setting direction for setting the dose, the biased resilient pre-delivery element relaxes before the drive member is displaced in the dose delivery direction for delivering the dose. When the resilient pre-delivery element relaxes, the piston rod is displaced with respect to the resilient pre-delivery element in the dose delivery direction by a pre-delivery distance. Furthermore, a piston rod is provided.