diff --git a/components/style/values/specified/box.rs b/components/style/values/specified/box.rs
index 2f114b5bb0a..11fbe6afb7b 100644
--- a/components/style/values/specified/box.rs
+++ b/components/style/values/specified/box.rs
@@ -106,8 +106,6 @@ pub enum DisplayInside {
     #[cfg(feature = "gecko")]
     MozDeck,
     #[cfg(feature = "gecko")]
-    MozGroupbox,
-    #[cfg(feature = "gecko")]
     MozPopup,
 }
 
@@ -231,8 +229,6 @@ impl Display {
     #[cfg(feature = "gecko")]
     pub const MozDeck: Self = Self::new(DisplayOutside::XUL, DisplayInside::MozDeck);
     #[cfg(feature = "gecko")]
-    pub const MozGroupbox: Self = Self::new(DisplayOutside::XUL, DisplayInside::MozGroupbox);
-    #[cfg(feature = "gecko")]
     pub const MozPopup: Self = Self::new(DisplayOutside::XUL, DisplayInside::MozPopup);
 
     /// Make a raw display value from <display-outside> and <display-inside> values.
@@ -623,8 +619,6 @@ impl Parse for Display {
             #[cfg(feature = "gecko")]
             "-moz-deck" if moz_display_values_enabled(context) => Display::MozDeck,
             #[cfg(feature = "gecko")]
-            "-moz-groupbox" if moz_display_values_enabled(context) => Display::MozGroupbox,
-            #[cfg(feature = "gecko")]
             "-moz-popup" if moz_display_values_enabled(context) => Display::MozPopup,
         })
     }