diff --git a/components/style/values/specified/box.rs b/components/style/values/specified/box.rs
index 2c56a32be54..b3a49d17bb0 100644
--- a/components/style/values/specified/box.rs
+++ b/components/style/values/specified/box.rs
@@ -1788,9 +1788,6 @@ pub enum Appearance {
     #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     MozWinExcludeGlass,
 
-    /// Titlebar elements on the Mac.
-    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
-    MozMacFullscreenButton,
     /// Mac help button.
     #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     MozMacHelpButton,