diff --git a/browser/themes/windows/browser.css b/browser/themes/windows/browser.css
index 4f960ae35aa69a1d1ce4ad368f5bae365229bbdf..a60d16adee588a1ab0d06d7676bbe80f179e088d 100644
--- a/browser/themes/windows/browser.css
+++ b/browser/themes/windows/browser.css
@@ -31,7 +31,6 @@
     /* stylelint-disable-next-line media-query-no-invalid */
     @media -moz-pref("widget.windows.mica.toplevel-backdrop", 2) {
       /* For acrylic, do the same we do for popups to guarantee some contrast */
-      background-color: light-dark(rgba(255, 255, 255, 0.6), rgba(0, 0, 0, 0.6));
     }
 
     /* Using a semitransparent background preserves the tinting from the backdrop.
@@ -60,14 +59,12 @@
 }
 
 /* This is needed for Windows 10, see bug 1961257 */
-@media (-moz-windows-accent-color-in-titlebar) {
-  :root[customtitlebar][sizemode="normal"] #navigator-toolbox {
+  :root[customtitlebar][sizemode="normal"] #browser {
     border-top: 0.5px solid ActiveBorder;
     &:-moz-window-inactive {
       border-top-color: InactiveBorder;
     }
   }
-}
 
 /* Titlebar */
 
