An anti-icing system for an aircraft nacelle includes an inner duct and an outer duct. The inner duct extends through a first bulkhead between a gas turbine engine and a plenum of the nacelle. The inner duct is configured to deliver heated gases from the gas turbine engine to the plenum. The outer duct includes a first end and a second end. The outer duct circumferentially encompasses at least a portion of the inner duct on a first side of the bulkhead. At least one of the first end and the second end of the outer duct is mounted to at least one of the respective first bulkhead and a second bulkhead by a bellows forming an annular seal between the respective bulkhead and the outer duct.