[Radiant] Using Sass mixins with Radiant managed Sass-filtered CSS files

[Wes Gamble]

 All,

I have a Sass file that  I am managing in Radiant.  I'd like to pull in 
a mixin to keep the Sass file clean.

I placed my mixin Sass file in 
RADIANT_ROOT/public/stylesheets/sass/_mixins.sass

I refer to it from my stylesheet with the import statement

  @import mixins.sass

and the file can't be found.

What am I doing wrong?

Thanks,
Wes