The invention relates to a gate valve assembly (20) for use in a subsea workover system comprising: —a valve block (22) having a flow path (21c); —valve seats (33, 34) located within the valve block (22) around a periphery of the flow path (21c), —a gate valve member (40) which is moveable across the flow path (21c) between a first position in which the flow path (21c) is open and a second position in which the flow path (21c) is closed; —said gate valve member (40) comprising a first portion (31) surrounding an opening (32) adapted to mate with the flow path (21c) when the gate valve member (40) is in the first position, said first portion (31) is provided with a cutting member (30) arranged on the periphery of the first portion (31) towards the opening (32). The gate valve member (40) further comprises a second portion (41) having at least one recessed part (42, 43), said recessed part (42, 43) being positioned such that when the gate valve member (40) is in the second position, the gate valve member (40) and the seats (33, 34) forms a sealing area (44, 45) arranged on a planar surface of the gate valve member (40).