We investigate the t = q k specialization of the homogeneous symmetric Macdonald polynomials P λ (X; q, t). We show an identity relating the polynomials P λ (X; q, q k ) and P λ ( 1−q 1−q k X; q, q k ). As a consequence, we describe an operator whose eigenvalues characterize the polynomials P λ (X; q, q k ).