// original

@import "mgmt/sprites/icons/*.png";
$icons: sprite-map("mgmt/sprites/icons/*.png");

.test {
  background: transparent $icons no-repeat 0 0;
}

// my test
$cc: sprite-map("sprites/icons/credit-cards/*.png")

[class^=credit-cards]
  background: $cc

// my output
[class^=credit-cards] {
  background: url('/assets/img/sprites/icons/credit-cards-sd348035735.png');