diff --git a/components/style/stylesheets/font_feature_values_rule.rs b/components/style/stylesheets/font_feature_values_rule.rs
index ba3396f589e..18cf957d466 100644
--- a/components/style/stylesheets/font_feature_values_rule.rs
+++ b/components/style/stylesheets/font_feature_values_rule.rs
@@ -53,7 +53,7 @@ pub trait ToGeckoFontFeatureValues {
 }
 
 /// A @font-feature-values block declaration value that keeps one value.
-#[derive(Clone, Debug, PartialEq)]
+#[derive(Clone, Debug, PartialEq, ToCss)]
 pub struct SingleValue(pub u32);
 
 impl Parse for SingleValue {
@@ -67,12 +67,6 @@ impl Parse for SingleValue {
     }
 }
 
-impl ToCss for SingleValue {
-    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
-        self.0.to_css(dest)
-    }
-}
-
 #[cfg(feature = "gecko")]
 impl ToGeckoFontFeatureValues for SingleValue {
     fn to_gecko_font_feature_values(&self, array: &mut nsTArray<u32>) {