Support for redistribution depends on whether inequality stems from differences in performance or luck, but different sources of luck may impact redistribution differentially. We elicit redistribution decisions from a U.S.-representative sample who observe worker earnings and whether luck influenced their earnings directly ("lucky outcomes") or indirectly by providing a relative advantage ("lucky opportunities"). Participants redistribute less under lucky opportunities. When assessing the impact of unequal opportunities, individuals rely on a heuristic that leads them to underestimate how even a small relative advantage can substantially influence worker earnings. Our findings highlight the role of inferential challenges in shaping attitudes towards inequality.