diff --git a/css/leptonChrome.css b/css/leptonChrome.css
index 13b6b7b..8f019f3 100644
--- a/css/leptonChrome.css
+++ b/css/leptonChrome.css
@@ -5133,6 +5133,13 @@
       visibility: unset !important;
       /* Makes the bookmarks toolbar visible if enabled */
     }
+
+    @media (-moz-gtk-csd-available) {
+      /* Fix transparent backgorund */
+      :root[tabsintitlebar][sizemode="fullscreen"] #TabsToolbar:not(:-moz-lwtheme) {
+        appearance: auto !important;
+      }
+    }
   }
 }
 /** Library - Icons Replace ***************************************************/
diff --git a/src/fullscreen/_index.scss b/src/fullscreen/_index.scss
index de46eaf..048b4fe 100644
--- a/src/fullscreen/_index.scss
+++ b/src/fullscreen/_index.scss
@@ -11,3 +11,10 @@
 :root[sizemode="fullscreen"] #PersonalToolbar[initialized="true"] {
   visibility: unset !important; /* Makes the bookmarks toolbar visible if enabled */
 }
+
+@include OS($linux) {
+  /* Fix transparent backgorund */
+  :root[tabsintitlebar][sizemode="fullscreen"] #TabsToolbar:not(:-moz-lwtheme) {
+    appearance: auto !important;
+  }
+}