When asked if she'll be back for season 5 of Sex Education, Mackey laughed: "Season 5? I've just finished the fourth one last week!
"No I don't think I'll be in season 5. I've said goodbye to Maeve."
Mackey had previously announced she would be in fewer scenes when Sex Education returns to Netflix.
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Speaking before production of the latest series, the actress said of filming season 4: "It feels very familiar! And it's a bit more sporadic because we have more characters. So there's… I'm not in it as consistently.
"But we're in the middle of filming now, and I'm excited to be back," she added. "And yeah, I'm intrigued to know what's going to happen – because I also don't know. I'm also finding out as we go along, so it'll be fun!"
Mackey isn't the only star to leave Sex Education in recent months, with Ncuti Gatwa announcing his departure just a couple of weeks ago.
The new Doctor Who actor posted a tribute to his character Eric on his Instagram, saying: "Last day. Last time. Bye bubs, thank you for all the lessons and for all the strength."
Additional reporting by Lauren Morris.