A process for increasing the hydrogen content of a synthesis gas including hydrogen and carbon oxides and having a carbon monoxide content≧45 mole % on a dry-gas basis, including the steps of: (i) combining the synthesis gas with steam to form a steam-enriched feed gas mixture (ii) passing the feed gas mixture at an inlet temperature in the range 220-370° C. over an iron-based water-gas shift catalyst to form a hydrogen-enriched shifted gas mixture having a carbon monoxide content≦10 mole % on a dry gas basis, and (iii) recovering the hydrogen-enriched shifted gas mixture, where a portion of the hydrogen-enriched shifted gas mixture is recycled to the feed gas mixture.