An injection device comprising - a pre-filled syringe comprising - a barrel (2.3) with an inner cavity (2.3.1) in fluid communication with - a hypodermic needle (2.1) attached to a distal end of the pre-filled syringe, - a piston (2.4) fluid-tightly sealing a proximal end of the inner cavity (2.3.1) and a safety device comprising - a support body (1.2) for retaining the pre-filled syringe therein, - an outer body (1.3) operably connected to the piston (2.4), - a needle shield (1.1), - a releasable retaining means wherein the needle shield (1.1), the support body (1.2) and the outer body (1.3) are telescopable relative to each other, wherein the piston (2.4) is movable in a distal direction to expel a medicament contained in the inner cavity (2.3.1) through the hypodermic needle (2.1) by a manual actuation of the outer body (1.3), wherein a telescoping movement of the outer body (1.3) with respect to the support body (1.2) is restricted by the retaining means when the needle shield (1.1) is moved with respect to the support body (1.2) in a proximal direction from an initial position surrounding the hypodermic needle (2.1) towards a retracted position where the hypodermic needle (2.1) protrudes from the needle shield (1.1), and wherein the retaining means is released when the needle shield (1.1) reaches the retracted position allowing for a telescoping movement of the outer body (1.3) with respect to the support body (1.2) to expel the medicament contained in the pre-filled syringe through the hypodermic needle (2.1), wherein the retaining means comprises a radial projection (1.2.3) connected to or being an integral part of one of the support body (1.2) or the outer body (1.3), characterized in that the retaining means comprises a longitudinal recess (1.3.2) formed into the other of the support body (1.2) or the outer body (1.3) and adapted to receive the radial projection (1.2.3), wherein the longitudinal recess (1.3.2) comprises a first section (1.3.2.1) and a second section (1.3.2.2) separated by a web (1.3.3) from each other, wherein the radial projection (1.2.3) engages the first section (1.3.2.1) of the longitudinal recess (1.3.2) to prevent the telescoping movement of the outer body (1.3) with respect to the support body (1.2) until the needle shield (1.1) has reached a retracted position, wherein the radial projection (1.2.3) has to overcome the web (1.3.3) before the outer body (1.3) is allowed to telescope with respect to the support body (1.2), wherein a retention force required to deflect the radial projection (1.2.3) exceeds a force required to move the needle shield (1.1) with respect to the support body (1.2) from the initial position to the retracted position. - a pre-filled syringe comprising - a barrel (2.3) with an inner cavity (2.3.1) in fluid communication with - a hypodermic needle (2.1) attached to a distal end of the pre-filled syringe, - a piston (2.4) fluid-tightly sealing a proximal end of the inner cavity (2.3.1) and a safety device comprising - a support body (1.2) for retaining the pre-filled syringe therein, - an outer body (1.3) operably connected to the piston (2.4), - a needle shield (1.1), - a releasable retaining means