The state estimation problem for linear systems with linear state equality constraints was dealt with in Ko & Bitmead [Ko, S., & Bitmead, R. (2007). State estimation for linear systems with state equality constraints. Automatica, 43, 1363-1368]. In this correspondence, it is first shown that a necessary assumption on the covariance of the process noise is missing in the main result of the paper. It is then shown that the main result of the paper can be achieved in a convenient and more general way without any additional assumptions on the covariance of the process noise except positive definiteness. (C) 2010 Elsevier Ltd. All rights reserved.