diff --git a/components/style/macros.rs b/components/style/macros.rs
index aeec5516fda..e2791e6f09f 100644
--- a/components/style/macros.rs
+++ b/components/style/macros.rs
@@ -5,7 +5,7 @@
 //! Various macro helpers.
 
 macro_rules! trivial_to_computed_value {
-    ($name: ident) => {
+    ($name:ty) => {
         impl $crate::values::computed::ToComputedValue for $name {
             type ComputedValue = $name;
 
diff --git a/components/style/values/computed/mod.rs b/components/style/values/computed/mod.rs
index 268baa23deb..46191a30400 100644
--- a/components/style/values/computed/mod.rs
+++ b/components/style/values/computed/mod.rs
@@ -4,7 +4,7 @@
 
 //! Computed values.
 
-use Atom;
+use {Atom, Namespace};
 use context::QuirksMode;
 use euclid::Size2D;
 use font_metrics::FontMetricsProvider;
@@ -332,13 +332,15 @@ impl<T> ToComputedValue for T
     }
 }
 
-trivial_to_computed_value!(Atom);
+trivial_to_computed_value!(());
+trivial_to_computed_value!(bool);
+trivial_to_computed_value!(f32);
+trivial_to_computed_value!(i32);
 trivial_to_computed_value!(u8);
 trivial_to_computed_value!(u16);
-trivial_to_computed_value!(bool);
-trivial_to_computed_value!(i32);
-trivial_to_computed_value!(f32);
+trivial_to_computed_value!(Atom);
 trivial_to_computed_value!(BorderStyle);
+trivial_to_computed_value!(Namespace);
 trivial_to_computed_value!(String);
 
 /// A `<number>` value.
diff --git a/components/style/values/specified/mod.rs b/components/style/values/specified/mod.rs
index 7c91096bb8b..9efed2e144f 100644
--- a/components/style/values/specified/mod.rs
+++ b/components/style/values/specified/mod.rs
@@ -21,7 +21,6 @@ use super::computed::{Context, ToComputedValue};
 use super::generics::{GreaterThanOrEqualToOne, NonNegative};
 use super::generics::grid::{GridLine as GenericGridLine, TrackBreadth as GenericTrackBreadth};
 use super::generics::grid::{TrackSize as GenericTrackSize, TrackList as GenericTrackList};
-use values::computed::ComputedValueAsSpecified;
 use values::specified::calc::CalcNode;
 
 pub use properties::animated_properties::TransitionProperty;
@@ -681,8 +680,8 @@ pub type NamespaceId = ();
 /// An attr(...) rule
 ///
 /// `[namespace? `|`]? ident`
-#[derive(Clone, Debug, Eq, PartialEq)]
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
+#[derive(Clone, Debug, Eq, PartialEq, ToComputedValue)]
 pub struct Attr {
     /// Optional namespace
     pub namespace: Option<(Namespace, NamespaceId)>,
@@ -777,5 +776,3 @@ impl ToCss for Attr {
         dest.write_str(")")
     }
 }
-
-impl ComputedValueAsSpecified for Attr {}