diff --git a/scss.inc.php b/scss.inc.php
index 5ad188cc..fe0cbd2b 100644
--- a/scss.inc.php
+++ b/scss.inc.php
@@ -2925,7 +2925,7 @@ protected function argumentDef(&$out) {
 			$arg = array($var[1], null);
 
 			$ss = $this->seek();
-			if ($this->literal(":") && $this->expression($defaultVal)) {
+			if ($this->literal(":") && $this->genericList($defaultVal, "expression")) {
 				$arg[1] = $defaultVal;
 			} else {
 				$this->seek($ss);
diff --git a/tests/inputs/mixins.scss b/tests/inputs/mixins.scss
index 0a90d538..7cb7e80f 100644
--- a/tests/inputs/mixins.scss
+++ b/tests/inputs/mixins.scss
@@ -57,3 +57,10 @@ div {
     color: $color;
 }
 
+@mixin linear-gradient($from, $to, $pos: left top) {
+  background-image: linear-gradient($pos, $from, $to);
+}
+
+div {
+    @include linear-gradient(red, green);
+}
diff --git a/tests/outputs/mixins.css b/tests/outputs/mixins.css
index 909210c6..1f07c755 100644
--- a/tests/outputs/mixins.css
+++ b/tests/outputs/mixins.css
@@ -25,3 +25,6 @@ div {
   color: white;
   color: blue;
   color: white; }
+
+div {
+  background-image: linear-gradient(left top, red, green); }