An annulus isolation valve assembly (1) being part of a tubing hanger assembly (100), with a valve bore (5) having a fluid mouth (9), and a sliding sleeve (11) which is arranged in the valve bore (5) and which has an axially extending sleeve bore (13). The sliding sleeve (11) has a radially facing sleeve port (17). A hydraulic piston (21) is functionally connected to the sliding sleeve (11). The sliding sleeve (11) comprises an axially facing fluid port (47) which is in fluid communication with the radially facing sleeve port (17).