There is provided an elongate aerosol-generating device having a polygonal transverse cross-section. The polygon includes at least six sides. The elongate aerosol-generating device includes a substrate receiving cavity configured to receive an aerosol-forming substrate, a heating element configured to heat an aerosol-forming substrate to generate an aerosol, and a power supply configured to provide power to the heating element. In addition, there is provided an aerosol-generating system, including the elongate aerosol-generating device, and a charging device including a cavity having a polygonal transverse cross-section corresponding to the polygonal transverse cross-section of the aerosol-generating device, the cavity being configured to receive the elongate aerosol-generating device.