A closure for closing in a sealing manner a distal opening on a syringe body is provided. The closure includes a fastening element that is or can be arranged on the syringe body around the distal opening and a closure cap that can be loosely connected to the fastening element and closing in a sealing manner the distal opening. The fastening element includes an inner thread that intermeshes with an outer thread on the closure cap, resulting in an initial state wherein the outer thread is formed on at least part of the closure cap. The part is under tension in such a way that after the closure cap is unscrewed from the inner thread the part under tension is pressed out over the inner thread of the fastening element such that the closure cap cannot be returned to the initial state once the closure cap is unscrewed.
