diff --git a/components/style/viewport.rs b/components/style/viewport.rs
index bbdd3a2ed35..2e965da4e54 100644
--- a/components/style/viewport.rs
+++ b/components/style/viewport.rs
@@ -69,7 +69,7 @@ macro_rules! declare_viewport_descriptor_inner {
         const VIEWPORT_DESCRIPTOR_VARIANTS: usize = $number_of_variants;
 
         impl ViewportDescriptor {
-            fn discriminant_value(&self) -> usize {
+            pub fn discriminant_value(&self) -> usize {
                 match *self {
                     $(
                         ViewportDescriptor::$assigned_variant(..) => $assigned_discriminant,
diff --git a/tests/unit/style/lib.rs b/tests/unit/style/lib.rs
index e2c2bbe7e28..f2be3da2307 100644
--- a/tests/unit/style/lib.rs
+++ b/tests/unit/style/lib.rs
@@ -3,7 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #![cfg(test)]
-#![feature(core_intrinsics, plugin, test)]
+#![feature(plugin, test)]
 
 extern crate app_units;
 extern crate cssparser;
diff --git a/tests/unit/style/viewport.rs b/tests/unit/style/viewport.rs
index 2ca9733afc2..026269421f7 100644
--- a/tests/unit/style/viewport.rs
+++ b/tests/unit/style/viewport.rs
@@ -51,13 +51,11 @@ fn test_meta_viewport<F>(meta: &str, callback: F)
     where F: Fn(&Vec<ViewportDescriptorDeclaration>, &str)
 {
     if let Some(mut rule) = ViewportRule::from_meta(meta) {
-        use std::intrinsics::discriminant_value;
-
         // from_meta uses a hash-map to collect the declarations, so we need to
         // sort them in a stable order for the tests
         rule.declarations.sort_by(|a, b| {
-            let a = unsafe { discriminant_value(&a.descriptor) };
-            let b = unsafe { discriminant_value(&b.descriptor) };
+            let a = a.descriptor.discriminant_value();
+            let b = b.descriptor.discriminant_value();
             a.cmp(&b)
         });