Percy Jackson author Rick Riordan has come out swinging after learning that online trolls have been criticizing Leah Jeffries for being cast in the role of Annabeth Chase in the new Disney+ series based on the wildly popular books. Jeffries previously Instagrammed a screencap of Variety‘s exclusive article on the casting announcement.

Jeffries’ casting was announced last week following the announcement that The Adam Project star, Walker Scobell, will take over the Percy Jackson role, which was previously played by Logan Lerman in the films that failed to take off as a franchise.

Here’s how Variety described Annabeth:

Annabeth is a true daughter of the Greek goddess, Athena. She is a brilliant strategist with an active and curious mind. After having spent the last five years at Camp Half-Blood, she longs to test her mettle in the human world, of which she barely remembers. She trains Percy to survive the mythological world, and in turn, he helps her connect with her humanity.

In the Percy Jackson films, Annabeth was played by Alexandra Daddario. In the new series coming to Disney+, Riordan, who authored the beloved book series, has more creative control this time around, and he wrote a lengthy post on his official website defending Jeffries’ casting, which he says was his decision.

“If you have a problem with this casting, however, take it up with me,” Riordan writes. “You have no one else to blame. Whatever else you take from this post, we should be able to agree that bullying and harassing a child online is inexcusably wrong. As strong as Leah is, as much as we have discussed the potential for this kind of reaction and the intense pressure this role will bring, the negative comments she has received online are out of line. They need to stop. Now.”

Riordan also reiterated that he was “quite clear a year ago” when he first announced the series that “we would be following Disney’s company policy on nondiscrimination.” The author did not pull his punches about the negative reactions to Jeffries’ casting, which he said they prepared for behind the scenes.

“You are judging her appropriateness for this role solely and exclusively on how she looks. She is a Black girl playing someone who was described in the books as white,” Riordan writes. “Friends, that is racism.”

(Via Rick Riordan)