diff --git a/src/sass/_colors.scss b/src/sass/_colors.scss
index 26ec674e..39d40c28 100644
--- a/src/sass/_colors.scss
+++ b/src/sass/_colors.scss
@@ -1,7 +1,12 @@
-@function gtkalpha($c,$a) {
-  @return unquote("alpha(#{$c},#{$a})");
+@function gtkalpha($c, $a) {
+  @if type-of($c) == 'color' {
+    @return rgba($c, $a);                     // objeto-cor quando $c é cor Sass
+  }
+  @return unquote("rgba(#{$c}, #{$a})");      // string para currentColor etc.
 }
 
+
+
 @function gtkmix($c1,$c2,$r) {
   $ratio: 1 -  $r / 100%; // match SCSS gtkmix()
   @return unquote("mix(#{$c1},#{$c2},#{$ratio})");