diff --git a/src/webui/www/private/css/Window.css b/src/webui/www/private/css/Window.css
index 2546a9dcb733..865fc80513cb 100644
--- a/src/webui/www/private/css/Window.css
+++ b/src/webui/www/private/css/Window.css
@@ -205,7 +205,7 @@ div.mochaToolbarWrapper.bottom {
 ---------------------------------------------------------------- */
 
 #modalOverlay {
-    background: hsla(0deg 0 0 / 30%);
+    background: hsl(0deg 0% 0% / 30%);
     display: none;
     left: 0;
     opacity: 0;