Wizard Alternate Class Feature?

[Viskocity]

I have a very distinct memory of a certain class feature which allows specialist transmuters to treat another spell as a if it were from the transmutation school. Unfortunately I have no idea where it came from. I have been searching the most likely books (complete mage/arcane) but haven't found it yet. My old grungy character sheet doesn't have a reference on it.

It is kind of important, because without it, my build becomes thoroughly impossible. Originally I was playing a transmuter with enchantment banned dipping mindbender, but obviously that becomes impossible.

Edit- Case closed! Thank you Zagan.

[zagan]

It's from UA but you can find it here.