On t-closedness of generalized power series rings

For an extension A⊆B of commutative rings, we present a sufficient condition for the ring A^S,?]] of generalized power series to be t-closed in B^S,?]], where (S,?) is a torsion-free cancellative ordered monoid. As a corollary, this result can be applied to the ring of power series in any number of indeterminates.