The invention relates to a solid, particulate, urea-based composition comprising urea in particulate form and a urease inhibitor of the type phosphoric triamide, in particular N-(n-butyl) thiophosphoric triamide (nBTPT), wherein the urea-based composition is further characterized in that it comprises one or more alkaline or alkaline-forming inorganic compounds. The composition according to the invention has been stabilized against the degradation of a urease inhibitor of the type phosphoric triamide, in particular N-(n-butyl) thiophosphoric triamide (nBTPT) in the presence of urea. The invention further relates to a method for the manufacture of the claimed solid, particulate, urea-based composition.