Problem with Compass generated gradients

/*----- SCSS File -----*/
@import "compass";

$experimental-support-for-mozilla: true;
$experimental-support-for-webkit: true;
$support-for-original-webkit-gradients: true;
$experimental-support-for-opera: true;
$experimental-support-for-microsoft: true;
$experimental-support-for-pie: true;

.more_button {
    @include single-text-shadow( -1px, -1px, 1px, false, #808080 );
    float: right;
    color: #fff;
    display: block;
    height: 24px;
    line-height: 24px;
    padding: 0 20px;
    font-size: 12px;
    margin-top: 3px;
    border: 1px solid #9e9e9e;
    @include background-image( linear-gradient( #c1c1c1, #a0a0a0 40%, #818181 ) );
}


/*----- Generated CSS -----*/
#main .more_button {
  text-shadow: -1px -1px 1px gray;
  float: right;
  color: #fff;
  display: block;
  height: 24px;
  line-height: 24px;
  padding: 0 20px;
  font-size: 12px;
  margin-top: 3px;
  border: 1px solid #9e9e9e;
  background-image: -webkit-gradient(linear, 50% 0%, 50% 100%, color-stop(0%, #c1c1c1), color-stop(40%, #a0a0a0), color-stop(100%, #818181));
  background-image: -webkit-linear-gradient(#c1c1c1, #a0a0a0 40%, #818181);
  background-image: -moz-linear-gradient(#c1c1c1, #a0a0a0 40%, #818181);
  background-image: -o-linear-gradient(#c1c1c1, #a0a0a0 40%, #818181);
  background-image: linear-gradient(#c1c1c1, #a0a0a0 40%, #818181);
}