The application relates to a needle protection assembly (1) comprising: —a supporting element (18) and a needle shield (8), —one locking element (20) located within said needle protection assembly (1) and not accessible to the user, —urging means (24) for displacing said needle shield (8), —a peg (19) located on said supporting element (18) or on said needle shield (8), and a cam (9) located on said needle shield (8) or on said supporting element (18), and—said locking element (20) is not formed by said peg (19) and cam (9). The respective longitudinal axis of the needle shield (8) and of the locking element (20) are merged when said needle shield (8) is in its before use or in use positions, and they form an angle (a) when said needle shield (8) is in its after use position.