Login as my old / new username ?

[Arylice]

I changed my username through the official forum https://atelier801.com/forums.

However, whenever I want to login in Transformice through Steam or through atelier801's forum,
I have to enter my old username, which is kind of weird...

While I am playing the game, I can see my new username,
but before entering the game, I still have to login with my old username.
Can someone help me figure this out, please?