The 13 year old was allowed to take one of the costumes she wears in the new film home and was hoping to wear it to go trick or treating.
But the star has had a growing spurt since filming wrapped on the movie – and can no longer slip into the superhero get-up.
She tells WENN, “I kept one of the 20 suits but I won’t fit into it for Halloween because I’m too tall now.
“It’s in my closet in a box to keep it pristine. I’ll have my kids wear it when I’m older.”
And Moretz is quietly happy she’ll never have to don the leather costume and mask again: “The suit was really uncomfortable… You can’t bend in leather, and so, whenever I would go down, the crotch would rip open… (In some scenes) if you look at the crotch, it has pieces of leather strapped in it and glued in.”