A cap assembly for a medicament delivery device, comprising: a cap having a tubular body defining an axially extending distal opening and configured to be mounted to a proximal end of a medicament delivery device, wherein the cap has a bottom structure defining a proximal end of the distal opening, and an elongated squeeze member configured to be received in the distal opening of the tubular body, and having a longitudinally extending channel configured to receive a delivery member shield, and which squeeze member has radial arms flexible in the radial direction and forming part of a wall of the channel, characterized in that the cap bottom structure has a cam structure provided inside the tubular body, and wherein the tubular body has inner walls provided with radial recesses; wherein the squeeze member has a proximal end face configured to cooperate with the cam structure of the cap, whereby axial displacement of the squeeze member from a first position in which the proximal end face bears against the cam structure to a second position in which the squeeze member is received further by the cap causes rotation of the squeeze member relative to the cap, wherein the radial arms are configured to engage with a respective radial recess of the tubular body in the first position of the squeeze member, and wherein the radial arms are configured to disengage from the respective radial recess when the squeeze member is displaced from the first position to the second position and rotated, whereby the flexible radial arms are pressed into the channel by the inner walls of the tubular body, reducing a cross-sectional area of the channel, wherein the cap assembly is configured to be assembled with a body of a medicament container assembly. a cap having a tubular body defining an axially extending distal opening and configured to be mounted to a proximal end of a medicament delivery device, wherein the cap has a bottom structure defining a proximal end of the distal opening, and an elongated squeeze member configured to be received in the distal opening of the tubular body, and having a longitudinally extending channel configured to receive a delivery member shield, and which squeeze member has radial arms flexible in the radial direction and forming part of a wall of the channel, wherein the squeeze member has a proximal end face configured to cooperate with the cam structure of the cap, whereby axial displacement of the squeeze member from a first position in which the proximal end face bears against the cam structure to a second position in which the squeeze member is received further by the cap causes rotation of the squeeze member relative to the cap, wherein the radial arms are configured to engage with a respective radial recess of the tubular body in the first position of the squeeze member, and wherein the radial arms are configured to disengage from the respective radial recess when the squeeze member is displaced from the first position to the second position and rotated, whereby the flexible radial arms are pressed into the channel by the inner walls of the tubular body, reducing a cross-sectional area of the channel, wherein the cap assembly is configured to be assembled with a body of a medicament container assembly.