Cannot login if the username is only one character

[linuxissuper]

I've installed gitlab with a user as admin whose username is only one character. I couldn't login and I thought I made some mistake or used the wrong password. But it seems a username with one character is just not possible in gitlab.

I've reinstalled gitlab for a new user with a two character long username and now it works

If this cannot be fixed, a hint or something at the installation phase would be good (I think)