diff --git a/browser/themes/linux/browser.css b/browser/themes/linux/browser.css
index 195cf888a61893cc9b0015e07e27bce94ec9d409..5f4cb6a1922730e8a0f1e9ad04169fb092917938 100644
--- a/browser/themes/linux/browser.css
+++ b/browser/themes/linux/browser.css
@@ -42,7 +42,8 @@
     -moz-default-appearance: -moz-window-decorations;
     appearance: auto;
 
-    #navigator-toolbox,
+    #zen-main-app-wrapper,
+    #zen-browser-background,
     dialog::backdrop {
       border-top-left-radius: env(-moz-gtk-csd-titlebar-radius);
       border-top-right-radius: env(-moz-gtk-csd-titlebar-radius);
@@ -50,13 +51,14 @@
 
     /* stylelint-disable-next-line media-query-no-invalid */
     @media -moz-pref("widget.gtk.rounded-bottom-corners.enabled") {
-      #navigator-toolbox {
+      #zen-main-app-wrapper {
         /* The body clip below covers this. */
         border-radius: 0;
       }
 
       body,
-      dialog::backdrop {
+      dialog::backdrop,
+      #zen-browser-background {
         /* Use an uniform clip to allow WebRender to optimize it better */
         border-radius: env(-moz-gtk-csd-titlebar-radius);
       }