A cartridge for use in an aerosol-generating system is provided, including a liquid storage portion including a housing configured to hold a liquid aerosol-forming substrate, the liquid storage portion including at least two parts in fluid communication with each other; a first part of the liquid storage portion including a heater assembly, a first capillary material, provided in contact with the heater assembly, and a second capillary material in contact with the first capillary material and spaced apart from the heater assembly by the first capillary material; and a second part of the liquid storage portion including a container configured to hold the liquid aerosol-forming substrate in liquid form to supply the liquid to the second capillary material.