Congruences for Siegel modular forms and their weights

J.-P. Serre proved that the congruences for elliptic modular forms mod p ^m descend to those of weights mod p ^m−1(p−1). Later, this result was generalized by T. Ichikawa to the case of Siegel modular forms. In this note we use elementary methods to reduce Ichikawa’s result to a similar question about elliptic modular forms with level, where results of Katz are available.