utf-8 character in non-english locale file throwing Encoding::CompatibilityError exception

Greetings!

I'm having a very strange problem I could use help understanding. I've
got 2 locale files: en.yml and fr.yml. When I have a utf-8 character
in the en.yml file it displays fine. When I put that exact same
character in the fr.yml file, I get an Encoding::CompatibilityError
exception

Here's the entry that's causing the problem:

firstname_placeholder: "Prénom"

I've tested with other characters and any utf-8 in the non-english
translation causes the same exception. Anybody got any idea why utf-8
works fine in the english locale file but not in the non-english file?

Thanks, Bill