The Chow rings of G2 and Spin(7) (vol 604, pg 137, 2007)

The result in our article ``The Chow rings of G(2) and Spin(7)'' depends on a computation by Yagita, who in turn ascribes a critical contribution, concerning the Chow ring of Spin(7), to Totaro. However in a private communication, Totaro has pointed out to me that he has not published the result anywhere. At the same time, he also explained that a recent paper of Yagita and Schuster gives an optimal counterexample to a conjecture of his on Chow rings - modulo the same result without a published proof. In this addendum, we give a direct proof for this missing ingredient. Using the notations and background of our aforementioned article, it is rather straightforward, and thus the proof fits well as a concluding point. Then we present the relationship with the article of Yagita and Schuster, and with Totaro's conjecture.