The invention relates to a container (1) for a waste heat utilization circuit (50), comprising a housing (2) delimiting a housing interior (3) such that the housing interior (3) can be flown through by a working medium (6), a sheath (4) arranged in the housing interior (3), in which an auxiliary medium (7) can be or is accommodated. According to the invention, the sheath (4) is fluid-tight, volume-variable, is designed at least in sections in a heat-conductive manner and delimits a sheath interior (5).