While many of us regard leather as our outerwear of choice, Sienna Miller is making a case for layering the luxe fabric under our favorite fall pieces. Stepping out in a crisp, ankle-grazing jumpsuit, Sienna proves that a sleeveless silhouette doesn’t have to be stashed this season—simply slip a form-fitting leather bodice underneath and the look instantly becomes seasonally appropriate. To ensure the effect doesn’t appear too bulky, opt for a top with ample stretch (more of a reason to go faux) and a jumpsuit that whittles at the waistline or can be belted. Furthermore, consider the neckline of your blouse in relation to the jumpsuit (opt for a mock or crew neck to ensure it doesn’t overcomplicate matters) and maintain a monochromatic neutral color palette. Finish with simple ankle-strap pumps and cool-girl shades for a polished autumn ensemble.