An aerosol-generating system comprising a liquid storage portion (20) comprising a rigid housing (24) holding a liquid aerosol-forming substrate, the housing having an opening and a fluid permeable heater assembly (30) comprising a plurality of electrically conductive filaments, wherein the fluid permeable heater assembly is fixed to the housing and extends across the opening of the housing. The provision of a heater assembly that extends across an opening of a liquid storage portion allows for a robust construction that is relatively simple to manufacture. This arrangement allows for a large contact area between the heater assembly and liquid aerosol-forming substrate. The heater assembly may be substantially flat allowing for simple manufacture.
