The final trailer for Fantastic Beasts: Crimes Of Grindelwald revealed South Korean actress Claudia Kim transforming from a woman into Voldemort’s snake.
Critics argued having an Asian actor play the role of Nagini, who is submissive to Voldemort in the Harry Potter books, was offensive.
One tweeted Rowling: “Listen Joanne, we get it, you didn’t include enough representation when you wrote the books.
“But suddenly making Nagini into a Korean woman is garbage.”
Rowling replied explaining that Nagini is a Naga, a “snake-like mythical creatures of Indonesian mythology”.
She added: “They are sometimes depicted as winged, sometimes as half-human, half-snake. Indonesia comprises a few hundred ethnic groups, including Javanese, Chinese and Betawi. Have a lovely day.”
Rowling later added she had been hiding the fact that Nagini was a Maledictus - a female who had been turned into an animal due to a blood curse - for 20 years.
It is not the first time the Harry Potter author has defended the film’s casting. Johnny Depp will play dark wizard Gellert Grindelwald, leading fans to complain after he was accused of domestic violence by his ex-wife Amber Heard in 2016.
Rowling admitted she had considered recasting the role but ultimately stuck with Depp, saying she was “genuinely happy to have Johnny playing a major character in the movies”.
Fantastic Beasts: The Crimes Of Grindelwald is the highly anticipated sequel to 2016’s Fantastic Beasts And Where To Find Them.
It will see Eddie Redmayne return as Newt Scamander while Jude Law plays a young Albus Dumbledore.
Fantastic Beasts: The Crimes of Grindelwald is due to be released in UK cinemas on November 16.