diff --git a/chrome/autohide_toolbox.css b/chrome/autohide_toolbox.css
index 58014ca..5d0e4fe 100644
--- a/chrome/autohide_toolbox.css
+++ b/chrome/autohide_toolbox.css
@@ -32,7 +32,8 @@ See the above repository for updates as well as full license text. */
   #navigator-toolbox:not(:-moz-lwtheme){ background-color: -moz-dialog !important; }
 }
 
-:root[sizemode="fullscreen"]{ margin-top: 0px !important; }
+:root[sizemode="fullscreen"],
+#navigator-toolbox[inFullscreen]{ margin-top: 0 !important; }
 
 #navigator-toolbox{
   position: fixed !important;