She might not be hitting the milestone birthday for another two months but writer Dawn O'Porter marked the occasion with several posts about the celebrations on Instagram.
Firstly, she uploaded a picture of her sister holding a birthday cake in the shape of a cat, with Dawn writing about how it as her sisters birthday and she had ''stole'' it and made her sister had a cake ''that looks like my beloved cat. It was so realistic it was emotional to cut.''
Then she posted an image of huge balloons spelling out happy birthday to...Dorn.
Yes, it appears that her husband, actor Chris O'Dowd, had spelled her name wrong.
She captioned the post, ''And yes, it was Chris who spelled DORN. 10 years of being together and he still can't get my name right.''
Her followers thought the whole party looked fantastic and that Chris' mishap was hilarious.
One wrote, ''That's my kind of party decor! Love it! Happy birthday.''
While another said, ''I just spat out my coffee laughing at Dorn! Husbands....good for a laugh. Happy birthday.''
Chris also posted a blurry snap of him and Dawn dancing as he kisses her cheek.
He captioned it, ''My lady had her 40th this weekend. There were some fashion choices made.''
She was in sparkles while he was rocking a leopard print jacket.
It looks like one hell of a party - Happy 4-0 Dawn.