Passing Variables to Mixins with "Variable Arguments" not possible

[tobstop]

$color-01: red;

@mixin box-shadow($shadow...) {
-webkit-box-shadow:$shadow;
-moz-box-shadow:$shadow;
box-shadow:$shadow;
}

.test {
@include box-shadow(0 0 4px rgba($color-01,0.2), inset 0 0 10px rgba(0,0,0,0.05));
}

is compiled to:
.test {
-webkit-box-shadow: 0 0 4px, inset 0 0 10px rgba(0, 0, 0, 0.05);
-moz-box-shadow: 0 0 4px, inset 0 0 10px rgba(0, 0, 0, 0.05);
box-shadow: 0 0 4px, inset 0 0 10px rgba(0, 0, 0, 0.05);
}

The color of the first box-shadow is missing.

It works if you don't use a variable for the color:

.test {
@include box-shadow(0 0 4px rgba(0,0,0,0.2), inset 0 0 10px rgba(0,0,0,0.05));
}

is compiled to:
.test {
-webkit-box-shadow: 0 0 4px rgba(0, 0, 0, 0.2), inset 0 0 10px rgba(0, 0, 0, 0.05);
-moz-box-shadow: 0 0 4px rgba(0, 0, 0, 0.2), inset 0 0 10px rgba(0, 0, 0, 0.05);
box-shadow: 0 0 4px rgba(0, 0, 0, 0.2), inset 0 0 10px rgba(0, 0, 0, 0.05);
}