diff --git a/chrome/show_window_title_in_menubar.css b/chrome/show_window_title_in_menubar.css
index da90101..7bda4b0 100644
--- a/chrome/show_window_title_in_menubar.css
+++ b/chrome/show_window_title_in_menubar.css
@@ -1,7 +1,7 @@
 /* Shows window title in menubar */
 /* Enable menubar for correct behavior */
 @-moz-document url(chrome://browser/content/browser.xhtml){
-  head{
+  :root:not([sizemode="fullscreen"]) > head{
     display: block;
     position: fixed;
     right: 140px; /* Space for window controls */