A connecting element for connecting two hollow bodies through which a fluid can flow comprises a first connecting part which can be brought into fluid-tight flow connection with a first hollow body through which a fluid can flow, a sealing element which is arranged at least partially in an inner area of the first connecting part and a locking element which is arranged on an outside of the first connecting part. The locking element can be transferred from an unlocked position into a locked position, wherein the locking element in the locked position acts upon the sealing element in such a way that an inside diameter of the sealing element is smaller than when the locking element is in the unlocked position.