diff --git a/chrome/toolbar/tabbar.css b/chrome/toolbar/tabbar.css
index f3a88d7..b1b92e6 100644
--- a/chrome/toolbar/tabbar.css
+++ b/chrome/toolbar/tabbar.css
@@ -22,6 +22,13 @@
   --tab-block-margin: 0px !important;
 }
 
+/* hide space above tabs when maximised for non-macOS versions of Firefox */
+@supports not -moz-bool-pref("layout.css.osx-font-smoothing.enabled") {
+  :root:is([inFullscreen], :not([tabsintitlebar]), [sizemode="maximized"]) #titlebar {
+    --tab-block-margin: 0px !important;
+  }
+}
+
 .tab-background {
 	border-radius: var(--tab-border-radius);
   border-bottom-left-radius: 0 !important;