Username with backslash causes 404 at /user/username

If a create a user with a backslash in the name, for example 'thisisau\sername', clicking the name in the top-right of the header takes me to a 404 page, trying to get to https://server:8080/user/thisisau/sername/.

If I replace the '/' in the URL username with '%5C' (encoded backslash) it successfully loads the user page.