A platform segment for supporting a nozzle guide vane for a gas turbine is provided. The platform segment includes a gas passage surface arranged to be in contact with a streaming gas exhausted from a combustor, wherein the streaming gas streams along the gas passage surface in a streaming direction, a cooling surface, opposite to and thermally connected to the gas passage surface and arranged to be in contact with a cooling fluid, a wall protruding from the cooling surface and extending at least partially in the streaming direction, wherein the wall is arranged circumferentially between positions, at which adjacent guide vanes are to be provided, such that cooling fluid is channeled by the wall for cooling a downstream portion of the cooling surface, and a further wall protruding from the cooling surface and extending at least partially in the streaming direction.