The present invention relates to a system and assembly for refilling a reservoir with liquid dispensed from a dispenser, in particular, but not exclusively, to a system and assembly for the substantially leak-free refilling of the reservoir of a smoking-substitute device with a liquid comprising nicotine from a refill dispenser. The assembly is configured to provide a gas communication pathway through the assembly and physically separate from the liquid communication pathway for venting gas from an end of the assembly proximal the first aperture to an exterior of the assembly responsive to the movement of the assembly to the secured and open configuration, the assembly configured to close the gas communication pathway in the unsecured and closed configuration.