Edited Unassigned: autoprefixer does not generate columns? [128]

I was able to get autoprefixer installed and running for SCSS and for most things it works great (flex, transition, box-sizing), however for columns I can't seem to get it to work for any browsers.

I've tried a couple different settings:
<add conditionalExpression="> 1% in US" />
<add conditionalExpression="last 2 versions" />
<add conditionalExpression="Firefox > 20" />

and none seem to be working. Any thoughts on what I can do to get Columns prefixing?

Edit:
To clarify, if we just write a single prefix, autoprefixer is not adding new prefixes.

We are using the SASS compiler. We have tested our code using Andrey Sitnik's Autoprefixer and gulp and everything works as expected in that it generates new prefixes.