A continuous process for reforming one or more hydrocarbons to a synthesis gas comprising hydrogen and carbon monoxide, the start-up phase of said process comprising (i) providing a reactor comprising a reaction zone which comprises a catalyst comprising a mixed oxide comprising cobalt and oxygen; (ii) continuously passing an inert gas stream through the reaction zone according to (i), said inert gas stream comprising one or more inert gases; (iii) continuously passing a reactant gas stream into the reaction zone obtained from (ii), wherein from 95 to 100 volume-% of the reactant gas stream passed into the reaction zone consist of the one or more hydrocarbons, carbon dioxide, and water; subjecting said reactant gas stream to reforming conditions in said reaction zone; and removing a product stream from said reaction zone, said product stream comprising hydrogen and carbon monoxide.