diff --git a/components/style/values/specified/box.rs b/components/style/values/specified/box.rs
index 76dd263e831..35552513cab 100644
--- a/components/style/values/specified/box.rs
+++ b/components/style/values/specified/box.rs
@@ -110,8 +110,6 @@ pub enum DisplayInside {
     #[cfg(feature = "gecko")]
     MozBox,
     #[cfg(feature = "gecko")]
-    MozStack,
-    #[cfg(feature = "gecko")]
     MozDeck,
     #[cfg(feature = "gecko")]
     MozPopup,
@@ -226,8 +224,6 @@ impl Display {
     #[cfg(feature = "gecko")]
     pub const MozInlineBox: Self = Self::new(DisplayOutside::Inline, DisplayInside::MozBox);
     #[cfg(feature = "gecko")]
-    pub const MozStack: Self = Self::new(DisplayOutside::XUL, DisplayInside::MozStack);
-    #[cfg(feature = "gecko")]
     pub const MozDeck: Self = Self::new(DisplayOutside::XUL, DisplayInside::MozDeck);
     #[cfg(feature = "gecko")]
     pub const MozPopup: Self = Self::new(DisplayOutside::XUL, DisplayInside::MozPopup);
@@ -608,8 +604,6 @@ impl Parse for Display {
             #[cfg(feature = "gecko")]
             "-moz-inline-box" if moz_box_display_values_enabled(context) => Display::MozInlineBox,
             #[cfg(feature = "gecko")]
-            "-moz-stack" if moz_display_values_enabled(context) => Display::MozStack,
-            #[cfg(feature = "gecko")]
             "-moz-deck" if moz_display_values_enabled(context) => Display::MozDeck,
             #[cfg(feature = "gecko")]
             "-moz-popup" if moz_display_values_enabled(context) => Display::MozPopup,