使用phpSASS Compass Extension

Question

I'm struggling to use the phpSASS compass extension.

I'm using the following code to create my css files, but it doesn't work when I try to @import anything from Compass:

require_once("libs/phpsass/SassParser.php");

$options = array(
'style' => 'nested',
'cache' => FALSE,
'syntax' => 'scss',
'debug' => TRUE,
'extensions' => array('Compass','Own')
);

$sass = new SassParser($options); 
$css = $sass->toCss( $scssFolder."/".$scssFile );

file_put_contents($cssFolder."/".$cssFile, $css);

Where am I going wrong?

NB. If I don't use Compass mixins then it works fine.