SELECT col INTO TEMP TABLE tab2 ON COMMIT DROP FROM tab1

why does this syntax fail in 9.5.3 please?

CREATE OR REPLACE FUNCTION play_game(
        IN in_uid integer,
        IN in_gid integer,
        IN in_tiles jsonb,
        OUT out_gid integer)
        RETURNS integer AS
$func$
DECLARE
        ....
BEGIN
        PERFORM check_positions(in_uid, in_gid, in_tiles);

        SELECT
                out_word AS word,
                max(out_score) AS score
        INTO TEMP TABLE _words ON COMMIT DROP
        FROM check_words(in_uid, in_gid, in_tiles)
        GROUP BY word, gid;

...

END
$func$ LANGUAGE plpgsql;