Web Essential for Visual Studio Sass compile wrong

问题:

I am using Visual Studio 2013 Update 4 and Web Essentials. I am coding a web site with Sass (scss) and I have problem with compile it. I have read many articles that Web Essentials doesn´t support it, but I found it works even in options.

But there is a problem, for example:

$primaryColor: #eeccff;

body {
  $primaryColor: #ccc;
  background: $primaryColor;
}

p {
  color: $primaryColor;
}

Paragraph (p) have color: #ccc, that is not correct.

Any advice?

Thanks.

EDIT: How can I upgrade the Sass compiler for Web Essentials?