_retina-image.scss in bourbon-4.0.2

- old
+ new

@@ -1,5 +1,5 @@
-@mixin retina-image($filename, $background-size, $extension: png, $retina-filename: null, $retina-suffix: _2x, $asset-pipeline: false) {
+@mixin retina-image($filename, $background-size, $extension: png, $retina-filename: null, $retina-suffix: _2x, $asset-pipeline: $asset-pipeline) {
   @if $asset-pipeline {
     background-image: image-url("#{$filename}.#{$extension}");
   }
   @else {
     background-image:       url("#{$filename}.#{$extension}");