diff --git a/components/style/properties/gecko.mako.rs b/components/style/properties/gecko.mako.rs
index b0953f9a1d9..1a6e0995fe0 100644
--- a/components/style/properties/gecko.mako.rs
+++ b/components/style/properties/gecko.mako.rs
@@ -1240,26 +1240,20 @@ fn static_assert() {
         <% self_grid = "self.gecko.mGridTemplate%s" % kind.title() %>
         use gecko::values::GeckoStyleCoordConvertible;
         use gecko_bindings::structs::{nsTArray, nsStyleGridLine_kMaxLine};
-        use nsstring::{nsCString, nsStringRepr};
+        use nsstring::nsStringRepr;
         use std::usize;
+        use values::CustomIdent;
         use values::generics::grid::TrackListType::Auto;
         use values::generics::grid::{RepeatCount, TrackSize};
 
         #[inline]
-        fn set_bitfield(bitfield: &mut u8, pos: u8, val: bool) {
-            let mask = 1 << (pos - 1);
-            *bitfield &= !mask;
-            *bitfield |= (val as u8) << (pos - 1);
-        }
-
-        #[inline]
-        fn set_line_names(servo_names: &[String], gecko_names: &mut nsTArray<nsStringRepr>) {
+        fn set_line_names(servo_names: &[CustomIdent], gecko_names: &mut nsTArray<nsStringRepr>) {
             unsafe {
                 bindings::Gecko_ResizeTArrayForStrings(gecko_names, servo_names.len() as u32);
             }
 
             for (servo_name, gecko_name) in servo_names.iter().zip(gecko_names.iter_mut()) {
-                gecko_name.assign_utf8(&nsCString::from(&*servo_name));
+                gecko_name.assign(servo_name.0.as_slice());
             }
         }
 
@@ -1284,8 +1278,8 @@ fn static_assert() {
 
         // Set defaults
         ${self_grid}.mRepeatAutoIndex = -1;
-        set_bitfield(&mut ${self_grid}._bitfield_1, 1, false);   // mIsAutoFill
-        set_bitfield(&mut ${self_grid}._bitfield_1, 2, false);   // mIsSubgrid
+        ${self_grid}.set_mIsAutoFill(false);
+        ${self_grid}.set_mIsSubgrid(false);
         // FIXME: mIsSubgrid is false only for <none>, but we don't support subgrid name lists at the moment.
 
         match v {
@@ -1297,7 +1291,7 @@ fn static_assert() {
                     let auto_repeat = track.auto_repeat.as_ref().expect("expected <auto-track-repeat> value");
 
                     if auto_repeat.count == RepeatCount::AutoFill {
-                        set_bitfield(&mut ${self_grid}._bitfield_1, 1, true);
+                        ${self_grid}.set_mIsAutoFill(true);
                     }
 
                     ${self_grid}.mRepeatAutoIndex = idx as i16;
diff --git a/components/style/values/generics/grid.rs b/components/style/values/generics/grid.rs
index 3cb10439598..3693c670718 100644
--- a/components/style/values/generics/grid.rs
+++ b/components/style/values/generics/grid.rs
@@ -5,7 +5,7 @@
 //! Generic types for the handling of
 //! [grids](https://drafts.csswg.org/css-grid/).
 
-use cssparser::{Parser, serialize_identifier};
+use cssparser::Parser;
 use parser::{Parse, ParserContext};
 use std::{fmt, mem, usize};
 use style_traits::{ToCss, ParseError, StyleParseError};
@@ -307,15 +307,15 @@ impl<L: ToComputedValue> ToComputedValue for TrackSize<L> {
 /// Helper function for serializing identifiers with a prefix and suffix, used
 /// for serializing <line-names> (in grid).
 pub fn concat_serialize_idents<W>(prefix: &str, suffix: &str,
-                                  slice: &[String], sep: &str, dest: &mut W) -> fmt::Result
+                                  slice: &[CustomIdent], sep: &str, dest: &mut W) -> fmt::Result
     where W: fmt::Write
 {
     if let Some((ref first, rest)) = slice.split_first() {
         dest.write_str(prefix)?;
-        serialize_identifier(first, dest)?;
+        first.to_css(dest)?;
         for thing in rest {
             dest.write_str(sep)?;
-            serialize_identifier(thing, dest)?;
+            thing.to_css(dest)?;
         }
 
         dest.write_str(suffix)?;
@@ -372,7 +372,7 @@ pub struct TrackRepeat<L> {
     /// If there's no `<line-names>`, then it's represented by an empty vector.
     /// For N `<track-size>` values, there will be N+1 `<line-names>`, and so this vector's
     /// length is always one value more than that of the `<track-size>`.
-    pub line_names: Vec<Vec<String>>,
+    pub line_names: Vec<Vec<CustomIdent>>,
     /// `<track-size>` values.
     pub track_sizes: Vec<TrackSize<L>>,
 }
@@ -502,7 +502,7 @@ pub struct TrackList<T> {
     /// If there's no `<line-names>`, then it's represented by an empty vector.
     /// For N values, there will be N+1 `<line-names>`, and so this vector's
     /// length is always one value more than that of the `<track-size>`.
-    pub line_names: Vec<Vec<String>>,
+    pub line_names: Vec<Vec<CustomIdent>>,
     /// `<auto-repeat>` value after computation. This field is necessary, because
     /// the `values` field (after computation) will only contain `<track-size>` values, and
     /// we need something to represent this function.
diff --git a/components/style/values/specified/grid.rs b/components/style/values/specified/grid.rs
index d19ab3703c3..9f68196d1b1 100644
--- a/components/style/values/specified/grid.rs
+++ b/components/style/values/specified/grid.rs
@@ -81,16 +81,13 @@ impl Parse for TrackSize<LengthOrPercentage> {
 /// Parse the grid line names into a vector of owned strings.
 ///
 /// https://drafts.csswg.org/css-grid/#typedef-line-names
-pub fn parse_line_names<'i, 't>(input: &mut Parser<'i, 't>) -> Result<Vec<String>, ParseError<'i>> {
+pub fn parse_line_names<'i, 't>(input: &mut Parser<'i, 't>) -> Result<Vec<CustomIdent>, ParseError<'i>> {
     input.expect_square_bracket_block()?;
     input.parse_nested_block(|input| {
         let mut values = vec![];
         while let Ok(ident) = input.try(|i| i.expect_ident()) {
-            if CustomIdent::from_ident((&*ident).into(), &["span"]).is_err() {
-                return Err(StyleParseError::UnspecifiedError.into())
-            }
-
-            values.push(ident.into_owned());
+            let ident = CustomIdent::from_ident(ident, &["span"])?;
+            values.push(ident);
         }
 
         Ok(values)