Would you consider going fur free?"
That's the challenge Sia issued to Kanye West, hours before he unveiled his latest fashion collection.
The pop star tweeted her question to Kanye, linking to a YouTube video that contained harrowing scenes of rabbits being slaughtered for their coats.
"This is the reality of fur ," said Sia. "It's so sad."
West's Yeezy Season 5 appeared to include both fur coats and accessories.
The most striking item was a floor-sweeping fur coat, showcased by hijab-wearing model Halima Aden, who was the first Miss Minnesota contestant to compete wearing a hijab and burkini.
Vogue magazine said the garments were faux fur, although the BBC has been unable to verify that report.
It is not the first time that Sia - who worked with Kanye on songs including Wolves and Reaper - has challenged celebrities over animal rights.
Last June, she tweeted the same video at Kanye's wife, Kim Kardashian, writing, "Hey @KimKardashian I think you're lovely. Would you consider going fur free? This is what animals go through for it."
In December, after rapper Azealia Banks posted an Instagram video apparently showing the remains of several chickens killed in a witchcraft ritual, Sia tweeted, "Sacrificing animals for your gain is the wackest [thing] I've ever heard."
The Australian singer is a vegan and supporter of animal rights' group Peta.
Kanye's show won praise from critics, who called it his most "demure" show yet and welcomed the fashion range's expanding colour palette - he added blues and reds to the line's traditional black and brown colour scheme.
Unlike last year's show - a massive production that required models to stand still for hours in the middle of a New York heatwave, causing some to faint - the Season 5 launch was decidedly low-key, with images projected one by one onto the surface of a giant black rectangle, from a live feed of models standing on a turntable backstage.
Photographers were not allowed - and Kanye didn't even appear to take a bow at the end of the 13-minute spectacle.
The audience, apparently conditioned to expect more drama at the rapper's fashion shows, remained seated for almost five minutes after the lights went up before finally shuffling out to their next appointment at New York Fashion Week.
Among those watching the launch were Kim Kardashian, Kylie Jenner, Hailey Baldwin, Zoe Kravitz, ASAP Ferg, Anna Wintour, Pusha T and Teyana Taylor.
The collection itself featured a lot of denim, paired with knee-high boots and a new shoe dubbed the Yeezy Runner.
Hoodies and bomber jackets also featured heavily, many sporting the Adidas stripes, while sweatshirts were stamped with the phrase Lost Hills - the name of Kanye's forthcoming album with Drake.