Minecraft big arms?

I have a slim skin inside every day, but suddenly I have a slim skin, a "classic" skin, so with the thicker arms.

Does anyone know how to fix this so that I could have normal & slim arms again? I also tried to change skins, sometimes this works and sometimes not, but even if it works with the skins, they are still classic.

So my question, does anyone know how to fix this?

Is on a bow near Mojang, think the fixxen soon.