A quick coupling for joining two fluid lines includes a first part which has a projection with a. sloping surface directed towards one axial end and a stop face directed towards the other axial end, and a second part which has at least one bracket with a catch that engages behind the stop face in a locked position. An assembly indicator is arranged next to the catch. In the locked position, the indicator projects outward beyond a catch segment of the bracket on which the catch is located, but, in the unlocked position, the indicator projects outward at most as far as the catch segment.