The invention relates to a continuous or repetitive batch process for the hydrogenation of levulinic acid (LA) or esters thereof to at least gamma valerolactone (GVL) in a reactor comprising a feed stream and an outlet stream, in the presence of a solid Ru catalyst, said process comprising (a) pretreating said solid Ru catalyst with a reductant; and (b) reacting levulinic acid with hydrogen and the pretreated solid Ru catalyst obtained in step (a) at a temperature and residence time suitable to form at least GVL, characterized in that the pretreatment is in the presence of a first solvent which comprises water. This process is stable and little or no Ru will leak form the support.