Basset/Assetic + SASS wont compile imports (osx)

问题

I am using Basset which in turn uses assetic for code minification and concatenation. I have the latest sass installed, using sass -v tells me it is 3.2.12

I have a css>sass folder and inside that a partials folder. The main.scss imports 2 files from the partials folder. One for variables (colours, widths etc) and the other for layout.

The partials begine with an underscore, so they should not be compiled (_variables.scss) . The main.scss looks like this:

@import "partials/variables";
@import "partials/layout";

partials/_variables.scss:

$bg: blue;

partials/_layout.scss:

body{
background-color: $bg;
}

When it tries to compile, assetic freaks out:

[Assetic\Exception\FilterException]
An error occurred while running:
'/usr/bin/ruby' '/usr/bin/sass' '--load-path' '/Users/Beans/Sites/testsite/public/assets/css/sass' '--scss' '--cache-location' '/private/var/folders/f4/xjby77695pbcgfdjfclfdqd40000gn/T' '/private/var/folders/f4/xjby77695pbcgfdjfclfdqd40000gn/T/assetic_sas
swcqUmJ'

Error Output:
Syntax error: Undefined variable: "$bg".
        on line 2 of /Users/Beans/Sites/testsite/public/assets/css/sass/partials/_layout.scss
        from line 2 of /private/var/folders/f4/xjby77695pbcgfdjfclfdqd40000gn/T/assetic_sasswcqUmJ
  Use --trace for backtrace.


Input:
@import "partials/variables";
@import "partials/layout";

I dont want to use less, i dont want to use laravel-guard (no collection support). I just want this to work!