Abstract: A ballast assembly for a fluorescent lighting fixture includes a magnetic core, a primary winding and a secondary winding, both windings mounted on a central leg of the core, with a shunt disposed between the windings to prevent a flux generated by the primary winding from coupling with a flux generated by the secondary winding. The ballast further includes means for securing the shunt comprising a wall placed between the windings, with the wall having one or more structures formed integrally on the wall for engaging the shunt. The wall may comprise a flange of a bobbin, or be free standing. Using formed structures eliminates the need for winding tape around the shunts to provide an air gap between the sunt and the core. This assures long-term stability and reduces the potential for nuisance humming.