A locking arrangement for detachably locking a cap (2; 22) on a container (1), the cap having a skirt (7) and the container (1) having an enclosure (4) opening into an opening (5), said locking arrangement comprising a number of keys (18) provided on the outside of said enclosure (4), a number of slots (9) provided on the inside of the skirt (7), and cooperative contact faces on the inside of the skirt (7) and on the outside of the enclosure (4), respectively, said keys (18) and slots (9) being provided in an area having a substantially circular cross section and defining a central axis, and each slot (9) having a locking section (10) for detachably locking a key (18). The cooperative contact faces are arranged to form an angle to each other, and the contact faces of the container (1) are provided at a greater distance from said central axis than the contact faces of the cap (2; 22), for forcing the cap (2; 22) and container (1) away from each other in opposite directions. The contact faces of the container are provided on protrusions declining in the direction towards the opening of the container, and the protrusions (16) are positioned adjacent to the keys (18) between the base (3) of the container (1) and the keys (18).