This paper deals with disturbance rejection, when the external disturbance signal is a chaotic process. We measure the amount of chaos by the Kolmogorov-Sinai entropy. The natural question is the extent to which the Kolmogorov-Sinai entropy is reduced by means of a feedback. This answer is that it is not possible to reduce the Kolmogorov-Sinai entropy by linear, stationary feedback if the open loop system is stable. In general, the Shannon entropy rate can't be decreased because of the Bode limitation.