The present invention relates to a dispensing mechanism for an aerosol-generating article, comprising an expandable buffering reservoir (16) with an inlet and an outlet, a dispensing reservoir (2) of constant volume with an inlet and an outlet, an inlet valve (18) connected to the inlet of the expandable buffering reservoir (16), wherein the inlet valve (18) is configured to be connected to a liquid storage portion (6) filled with pressurized liquid such that the liquid can only flow from the liquid storage portion (6) to the expandable buffering reservoir (16), an outlet valve (8) connecting the outlet of the expandable buffering reservoir (16) to the inlet of the dispensing reservoir (2) such that liquid can only flow from the expandable buffering reservoir (16) to the dispensing reservoir (2), and a volume modifier (4) configured to modify the volume of the expandable buffering reservoir (16), wherein expanding a current volume of the expandable buffering reservoir (16) to an expanded volume causes a drawing of liquid from the liquid storage portion (6) to the expandable buffering reservoir (16) until the expanded volume of the expandable buffering reservoir (16) is filled up with the liquid, and wherein compressing the expanded volume of the expandable buffering reservoir (16) causes an expelling of liquid from the expandable buffering reservoir (16) to the dispensing reservoir (2) until the dispensing reservoir (2) is filled up with the liquid. Furthermore, the dispensing reservoir (2) is configured to release its content of liquid during one puff of a user.
