There is provided a cartridge for an aerosol-generating system, including a housing configured to hold an aerosol-forming substrate and having an opening; and a heater assembly including at least one heater element fixed to the housing and extending across the opening of the housing, wherein the at least one heater element defines a plurality of apertures configured to allow fluid to pass through the at least one heater element, and wherein apertures of the plurality of apertures have different sizes. There is also provided an aerosol-generating system, including an aerosol-generating device and the cartridge. And, there is provided a method of manufacturing a cartridge for an aerosol-generating system.