diff --git a/components/style/stylesheets/font_feature_values_rule.rs b/components/style/stylesheets/font_feature_values_rule.rs
index b0d94e3e206..f27ac9b6d3d 100644
--- a/components/style/stylesheets/font_feature_values_rule.rs
+++ b/components/style/stylesheets/font_feature_values_rule.rs
@@ -118,7 +118,8 @@ impl ToGeckoFontFeatureValues for PairValues {
 }
 
 /// A @font-feature-values block declaration value that keeps a list of values.
-#[derive(Clone, Debug, PartialEq)]
+#[css(iterable)]
+#[derive(Clone, Debug, PartialEq, ToCss)]
 pub struct VectorValues(pub Vec<u32>);
 
 impl Parse for VectorValues {
@@ -145,24 +146,6 @@ impl Parse for VectorValues {
     }
 }
 
-impl ToCss for VectorValues {
-    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
-    where
-        W: Write,
-    {
-        let mut iter = self.0.iter();
-        let first = iter.next();
-        if let Some(first) = first {
-            first.to_css(dest)?;
-            for value in iter {
-                dest.write_char(' ')?;
-                value.to_css(dest)?;
-            }
-        }
-        Ok(())
-    }
-}
-
 #[cfg(feature = "gecko")]
 impl ToGeckoFontFeatureValues for VectorValues {
     fn to_gecko_font_feature_values(&self, array: &mut nsTArray<u32>) {