CodePen: 'rebem-css' is not a valid postcss plugin

[ilyar]

Setup

CSS Preprocessor: PostCSS http://codepen.io/ilyar/pen/dvJVaa

Actual result

http://codepen.io/ilyar/pen/dvJVaa.css

@use rebem-css;

:block(block)
{
   color: #0f0;
}
// 'rebem-css' is not a valid postcss plugin.

Expected Result

.block
{
   color: #0f0;
}