A medicament delivery device (1; 1-1; 1'; 1'-1) for injection of a medicament, comprising: a housing (5; 5-1; 5'; 5") arranged to receive a medicament container assembly (3; 3'), an activation member (7; 7-1; 7'; 7") axially movable relative to the housing (5; 5-1; 5'; 5") between an extended position and a retracted position to expel medicament from the medicament container assembly(3; 3'), which activation member (7; 7-1; 7'; 7") comprises gripping means (7d; 7'd), and wherein the housing (5; 5-1; 5'; 5") and the activation member (7; 7-1; 7'; 7") comprise a movement guide mechanism comprising a first guide in the form of a track, a second guide defined by an external surface of a side wall of said track, which external surface has a locking portion, a guide channel extending from the first guide to the second guide merging the first guide with the second guide, and a guide follower, wherein the guide follower is arranged to slide in the track of the first guide when the activation member (7; 7-1; 7'; 7") is moved from the extended position to the retracted position for expelling medicament, entering the guide channel whereby the guide follower is shifted from the first guide to the second guide, wherein the gripping means (7d; 7'd) is arranged to engage the medicament container assembly (3; 3') when the activation member (7; 7-1; 7'; 7") is in the retracted position, and wherein the guide follower is arranged to slide along the second guide when the activation member (7; 7-1; 7'; 7") is moved back from the retracted position to the extended position, and wherein the locking portion is arranged to interact with the guide follower when the activation member (7; 7-1; 7'; 7") has been moved back from the retracted position to the extended position to restrict movement of the activation member (7; 7-1; 7'; 7") relative to the housing (5; 5-1; 5'; 5"). a housing (5; 5-1; 5'; 5") arranged to receive a medicament container assembly (3; 3'), an activation member (7; 7-1; 7'; 7") axially movable relative to the housing (5; 5-1; 5'; 5") between an extended position and a retracted position to expel medicament from the medicament container assembly(3; 3'), which activation member (7; 7-1; 7'; 7") comprises gripping means (7d; 7'd), and wherein the housing (5; 5-1; 5'; 5") and the activation member (7; 7-1; 7'; 7") comprise a movement guide mechanism comprising a first guide in the form of a track, a second guide defined by an external surface of a side wall of said track, which external surface has a locking portion, a guide channel extending from the first guide to the second guide merging the first guide with the second guide, and a guide follower, wherein the guide follower is arranged to slide in the track of the first guide when the activation member (7; 7-1; 7'; 7") is moved from the extended position to the retracted position for expelling medicament, entering the guide channel whereby the guide follower is shifted from the first guide to the second guide, wherein the gripping means (7d; 7'd) is arranged to engage the medicament container assembly (3; 3') when the activation member (7; 7-1; 7'; 7") is in the retracted position, and wherein the guide follower is arranged to slide along the second guide when the activation member (7; 7-1; 7'; 7") is moved back from the retracted position to the extended position, and wherein the locking portion is arranged to interact with the guide follower when the activation member (7; 7-1; 7'; 7") has been moved back from the retracted position to the extended position to restrict movement of the activation member (7; 7-1; 7'; 7") relative to the housing (5; 5-1; 5'; 5").