Potential Error in CSS Flexbox Challenge

Hello everyone

for the past two days, every time I run the tests, it returns the following error message:

Your .follow-btn should have a display property set to flex.

This is fine by itself, but my code looks like this:

header .follow-btn {
margin: 0 0 0 auto;
display: flex;
}

Am I doing something wrong or is this a bug?

Thanks

Marie