diff --git a/components/style/values/specified/box.rs b/components/style/values/specified/box.rs
index 1fea857d3e8..de6e8da1205 100644
--- a/components/style/values/specified/box.rs
+++ b/components/style/values/specified/box.rs
@@ -389,20 +389,11 @@ impl Display {
                 };
                 Display::from3(DisplayOutside::Block, inside, self.is_list_item())
             },
-            // If this pref is true, then we'll blockify "-moz-inline-box" to
-            // "-moz-box", and blockify "-moz-box" to itself. Otherwise, we
-            // blockify both to "block".
             #[cfg(feature = "gecko")]
             DisplayOutside::XUL => {
-                if static_prefs::pref!(
-                    "layout.css.xul-box-display-values.survive-blockification.enabled"
-                ) {
-                    match self.inside() {
-                        DisplayInside::MozInlineBox | DisplayInside::MozBox => Display::MozBox,
-                        _ => Display::Block,
-                    }
-                } else {
-                    Display::Block
+                match self.inside() {
+                    DisplayInside::MozInlineBox | DisplayInside::MozBox => Display::MozBox,
+                    _ => Display::Block,
                 }
             },
             DisplayOutside::Block | DisplayOutside::None => *self,