Repeat after “Percy Jackson” author Rick Riordan: “Leah Jeffries is Annabeth Chase.”

Riordan has condemned a racist backlash to the recently announced cast of “Percy Jackson & the Olympians,” the forthcoming Disney+ series based on his book saga of the same name. In a blog post published Tuesday, the bestselling novelist implored people to stop attacking Jeffries, the young Black actor playing Annabeth, who was described as white in the books.

“The response to the casting of Leah has been overwhelmingly positive and joyous, as it should be,” Riordan wrote. “Leah brings so much energy and enthusiasm to this role, so much of Annabeth’s strength. She will be a role model for new generations of girls who will see in her the kind of hero they want to be.

“If you have a problem with this casting, however, take it up with me. 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.”

Earlier this month, Disney announced that Jeffries and Aryan Simhadri had landed the coveted roles of Annabeth Chase and Grover Underwood, respectively. In the “Percy Jackson” novels, Annabeth and Grover are the best friends of Percy, who will be portrayed by Walker Scobell.

The first book in Riordan’s fantasy series, “The Lightning Thief,” sees Percy meet Annabeth at Camp Half-Blood, a retreat for demigod children of the Greek gods. Annabeth is the sharp-witted daughter of Athena, goddess of wisdom, while Percy is the courageous son of Poseidon, god of the sea. Grover is a cautious satyr who embarks on daring mythological journeys alongside Percy and Annabeth.

“I was quite clear a year ago, when we announced our first open casting, that we would be following Disney’s company policy on nondiscrimination,” Riordan continued in his blog post.

“I have been clear, as the author, that I was looking for the best actors to inhabit and bring to life the personalities of these characters, and that physical appearance was secondary for me. We did that. We took a year to do this process thoroughly and find the best of the best. This trio is the best.”

Since booking “Percy Jackson,” 12-year-old Jeffries also has garnered enthusiastic support from “The White Lotus” star Alexandra Daddario, who originated the role of Annabeth onscreen in the 2010 film adaptation of “The Lightning Thief.” On Twitter this week, Daddario predicted that Jeffries “is going to be an incredible Annabeth.”

“Once you see Leah as Annabeth, she will become exactly the way you imagine Annabeth, assuming you give her that chance, but you refuse to credit that this may be true,” Riordan wrote.

“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. Friends, that is racism.”

In 2015, Jeffries made her small-screen debut as Lola Lyon on the musical series “Empire.” She later played the onscreen daughter of Lil Rel Howery in the Fox comedy “Rel.” Up next, she’ll appear in the film “Beast” opposite Idris Elba.

On Instagram, a “confident” and undeterred Jeffries also addressed the casting complaints in a video message advising her haters to stop “wasting time” by trying to bring her down because “it’s not gonna work.”

In a press release this month, Disney revealed that production on “Percy Jackson” will begin soon in Vancouver, Canada. Executive producers Riordan and Jon Steinberg will co-write the pilot episode, directed by James Bobin.

“The core message of Percy Jackson has always been that difference is strength,” Riordan concluded his statement. “You should never judge someone by how well they fit your preconceived notions. That neurodivergent kid who has failed out of six schools, for instance, may well be the son of Poseidon. Anyone can be a hero.

“If you don’t get that, if you’re still upset about the casting of this marvelous trio, then it doesn’t matter how many times you have read the books. You didn’t learn anything from them.”