A spinning unit of an air jet spinning machine with a spinning nozzle, which serves the purpose of producing a yarn from a fiber composite fed to the spinning nozzle. The spinning nozzle features an inlet for the fiber composite, an internal vortex chamber, a yarn formation element protruding into the vortex chamber along with an outlet for the yarn produced inside the vortex chamber. The spinning unit is allocated with an additive supply, which is designed to supply the spinning nozzle with an additive. The additive supply includes at least one top frame fixed on the spinning nozzle, through which the additive is able to be fed to the spinning nozzle. In addition, a top frame for fixing on a spinning nozzle of an air jet spinning machine is proposed.