The present invention concerns a mechanism for a drug delivery device, having a longitudinal axis and comprising a first member comprising a first contact surface and a second member comprising a second contact surface, wherein the first member is configured to be assembled to the second member, wherein the first member and the second member are configured such that the first contact surface abuts the second contact surface when the first member is assembled to the second member, wherein the first contact surface is arranged such that a force applied to the mechanism in a direction parallel to the longitudinal axis is split up into a first component in a direction perpendicular to a surface normal of the first contact surface and a second component parallel to the surface normal, wherein the first member and the second member are configured such that the first member is detached from the second member by the force applied to the mechanism in a direction parallel to the longitudinal axis if the absolute value of the force is stronger than a first predetermined value, and wherein the first predetermined value is defined as the absolute value of the force which has a first component strong enough to move the first contact surface out of abutment with the second member.