After upgrade the forum shows full-width when logged in

Recently upgraded two forums to 3.2.0.beta3-dev and now logged out the forum shows as it always has with the content centred (normal behaviour, and as seen here on meta) but when logged in it goes to full width:

Using a Mac with Safari and FireFox. Also tried creating a new style but the same thing happens and it is happening on both forums. Is there a new setting for this or is it a bug of some sort?