diff --git a/src/mui/core/styles/Styles.hx b/src/mui/core/styles/Styles.hx
index 63d8fc4..db4f6d9 100644
--- a/src/mui/core/styles/Styles.hx
+++ b/src/mui/core/styles/Styles.hx
@@ -1,5 +1,6 @@
 package mui.core.styles;
 
+import mui.Colors.ColorString;
 #if !macro
 import haxe.extern.EitherType;
 import js.Object;
@@ -14,6 +15,7 @@ import haxe.macro.Expr;
 
 @:jsRequire('@material-ui/core/styles')
 extern class Styles {
+	extern static function alpha(color:ColorString, opacity:Float):ColorString;
 	public static inline macro function jss(styles:Expr) {
 		return switch (styles.expr) {
 			case EObjectDecl(fields):