There is provided an aerosol generating system for heating a liquid aerosol-forming substrate. The system includes a liquid storage portion (113) for storing the liquid aerosol-forming substrate (115), and leakage prevention means configured to prevent or reduce leakage of the liquid aerosol-forming substrate from the liquid storage portion. The leakage prevention means may comprise one or more of a porous plug at least partially located within the liquid storage portion, sealing means between the liquid storage portion and a capillary wick (117), and sealing means between the liquid storage portion and an electrical connector of an electric heater (119).