diff --git a/servo/components/style/properties/longhand/font.mako.rs b/servo/components/style/properties/longhand/font.mako.rs
index 191dca525742a..dc9814c182904 100644
--- a/servo/components/style/properties/longhand/font.mako.rs
+++ b/servo/components/style/properties/longhand/font.mako.rs
@@ -1315,6 +1315,7 @@ ${helpers.single_keyword_system("font-kerning",
     }
 </%helpers:longhand>
 
+#[cfg(any(feature = "gecko", feature = "testing"))]
 macro_rules! exclusive_value {
     (($value:ident, $set:expr) => $ident:ident) => {
         if $value.intersects($set) {