diff --git a/components/style/values/generics/grid.rs b/components/style/values/generics/grid.rs
index 68049274c12..b627231ecd5 100644
--- a/components/style/values/generics/grid.rs
+++ b/components/style/values/generics/grid.rs
@@ -200,12 +200,12 @@ impl<L: ToComputedValue> ToComputedValue for TrackBreadth<L> {
     }
 }
 
-#[derive(Clone, Debug, HasViewportPercentage, PartialEq)]
-#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
 /// A `<track-size>` type for explicit grid track sizing. Like `<track-breadth>`, this is
 /// generic only to avoid code bloat. It only takes `<length-percentage>`
 ///
 /// https://drafts.csswg.org/css-grid/#typedef-track-size
+#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
+#[derive(Clone, Debug, HasViewportPercentage, PartialEq, ToCss)]
 pub enum TrackSize<L> {
     /// A flexible `<track-breadth>`
     Breadth(TrackBreadth<L>),
@@ -213,10 +213,12 @@ pub enum TrackSize<L> {
     /// and a flexible `<track-breadth>`
     ///
     /// https://drafts.csswg.org/css-grid/#valdef-grid-template-columns-minmax
+    #[css(comma, function)]
     Minmax(TrackBreadth<L>, TrackBreadth<L>),
     /// A `fit-content` function.
     ///
     /// https://drafts.csswg.org/css-grid/#valdef-grid-template-columns-fit-content
+    #[css(function)]
     FitContent(L),
 }
 
@@ -259,26 +261,6 @@ impl<L: PartialEq> TrackSize<L> {
     }
 }
 
-impl<L: ToCss> ToCss for TrackSize<L> {
-    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
-        match *self {
-            TrackSize::Breadth(ref b) => b.to_css(dest),
-            TrackSize::Minmax(ref infexible, ref flexible) => {
-                dest.write_str("minmax(")?;
-                infexible.to_css(dest)?;
-                dest.write_str(", ")?;
-                flexible.to_css(dest)?;
-                dest.write_str(")")
-            },
-            TrackSize::FitContent(ref lop) => {
-                dest.write_str("fit-content(")?;
-                lop.to_css(dest)?;
-                dest.write_str(")")
-            },
-        }
-    }
-}
-
 impl<L: ToComputedValue> ToComputedValue for TrackSize<L> {
     type ComputedValue = TrackSize<L::ComputedValue>;