Can't login to AppleID using Yubikey on Firefox

I turned on Security Key support for my AppleID and registered all 3 of my Yubikeys. Everything has been working great, except when I try to login to appleid.apple.com. It takes my username and password, and prompts me to insert my Security Key and click the button the screen. I do that and then I get a message that "This browser does not support security keys." I use my Yubikeys just fine with Google, Twitter, Facebook, Github and every other site I try them on.

Does anyone else have this problem with Yubikeys and Firefox?