Sulfur addition is used to probe the role of gold in Au/Fe2O3/ZrO2 catalyst in the water-gas shift (WGS) at high temperature (623-773 K) and pressure (21 bar). Sulfur poisoning unravels the WGS activity contribution by gold nano-particles and gold promotion of iron oxide in Au/Fe2O3/ZrO2. The active site(s) on gold nano-particles are poisoned by sulfur, which is reflected in a suppressed WGS activity of presulfided Au/ZrO2. The same holds for the WGS activity contribution of gold nano-particles in Au/Fe2O3/ZrO2, but the promotion by gold of the Fe2O3 is still present after presulfidation. The WGS performance of Fe2O3/ZrO2 and Au/ZrO2 catalysts with and without sulfur pretreatment are also compared with that of Au/Fe2O3/ZrO2. (C) 2016 Elsevier B.V. All rights reserved.