diff --git a/components/script/dom/element.rs b/components/script/dom/element.rs
index 24eda14cab5..88366f591d2 100644
--- a/components/script/dom/element.rs
+++ b/components/script/dom/element.rs
@@ -171,14 +171,14 @@ pub trait RawLayoutElementHelpers {
 
 #[inline]
 #[allow(unsafe_code)]
-unsafe fn get_attr_for_layout<'a>(elem: &'a Element, namespace: &Namespace, name: &Atom) -> Option<&'a JS<Attr>> {
+unsafe fn get_attr_for_layout(elem: &Element, namespace: &Namespace, name: &Atom) -> Option<LayoutJS<Attr>> {
     // cast to point to T in RefCell<T> directly
     let attrs = elem.attrs.borrow_for_layout();
     attrs.iter().find(|attr: & &JS<Attr>| {
         let attr = attr.to_layout().unsafe_get();
         *name == (*attr).local_name_atom_forever() &&
         (*attr).namespace() == namespace
-    })
+    }).map(|attr| attr.to_layout())
 }
 
 #[allow(unsafe_code)]
@@ -187,8 +187,7 @@ impl RawLayoutElementHelpers for Element {
     unsafe fn get_attr_val_for_layout<'a>(&'a self, namespace: &Namespace, name: &Atom)
                                           -> Option<&'a str> {
         get_attr_for_layout(self, namespace, name).map(|attr| {
-            let attr = attr.to_layout().unsafe_get();
-            (*attr).value_ref_forever()
+            (*attr.unsafe_get()).value_ref_forever()
         })
     }
 
@@ -208,40 +207,22 @@ impl RawLayoutElementHelpers for Element {
     #[inline]
     unsafe fn get_attr_atom_for_layout(&self, namespace: &Namespace, name: &Atom)
                                       -> Option<Atom> {
-        let attrs = self.attrs.borrow_for_layout();
-        (*attrs).iter().find(|attr: & &JS<Attr>| {
-            let attr = attr.to_layout().unsafe_get();
-            *name == (*attr).local_name_atom_forever() &&
-            (*attr).namespace() == namespace
-        }).and_then(|attr| {
-            let attr = attr.to_layout().unsafe_get();
-            (*attr).value_atom_forever()
+        get_attr_for_layout(self, namespace, name).and_then(|attr| {
+            (*attr.unsafe_get()).value_atom_forever()
         })
     }
 
     #[inline]
     unsafe fn has_class_for_layout(&self, name: &Atom) -> bool {
-        let attrs = self.attrs.borrow_for_layout();
-        (*attrs).iter().find(|attr: & &JS<Attr>| {
-            let attr = attr.to_layout().unsafe_get();
-            (*attr).local_name_atom_forever() == atom!("class")
-        }).map_or(false, |attr| {
-            let attr = attr.to_layout().unsafe_get();
-            (*attr).value_tokens_forever().map(|tokens| {
-                tokens.iter().any(|atom| atom == name)
-            })
-        }.take().unwrap())
+        get_attr_for_layout(self, &ns!(""), &atom!("class")).map_or(false, |attr| {
+            (*attr.unsafe_get()).value_tokens_forever().unwrap().iter().any(|atom| atom == name)
+        })
     }
 
     #[inline]
     unsafe fn get_classes_for_layout(&self) -> Option<&'static [Atom]> {
-        let attrs = self.attrs.borrow_for_layout();
-        (*attrs).iter().find(|attr: & &JS<Attr>| {
-            let attr = attr.to_layout().unsafe_get();
-            (*attr).local_name_atom_forever() == atom!("class")
-        }).and_then(|attr| {
-            let attr = attr.to_layout().unsafe_get();
-            (*attr).value_tokens_forever()
+        get_attr_for_layout(self, &ns!(""), &atom!("class")).map(|attr| {
+            (*attr.unsafe_get()).value_tokens_forever().unwrap()
         })
     }
 
diff --git a/tests/wpt/mozilla/meta/MANIFEST.json b/tests/wpt/mozilla/meta/MANIFEST.json
index de093bd00a2..efd18936509 100644
--- a/tests/wpt/mozilla/meta/MANIFEST.json
+++ b/tests/wpt/mozilla/meta/MANIFEST.json
@@ -14,6 +14,20 @@
   "local_changes": {
     "deleted": [],
     "items": {
+      "reftest": {
+        "css/class-namespaces.html": [
+          {
+            "path": "css/class-namespaces.html",
+            "references": [
+              [
+                "/_mozilla/css/class-namespaces-ref.html",
+                "=="
+              ]
+            ],
+            "url": "/_mozilla/css/class-namespaces.html"
+          }
+        ]
+      },
       "testharness": {
         "mozilla/DOMParser.html": [
           {
@@ -515,7 +529,20 @@
         ]
       }
     },
-    "reftest_nodes": {}
+    "reftest_nodes": {
+      "css/class-namespaces.html": [
+        {
+          "path": "css/class-namespaces.html",
+          "references": [
+            [
+              "/_mozilla/css/class-namespaces-ref.html",
+              "=="
+            ]
+          ],
+          "url": "/_mozilla/css/class-namespaces.html"
+        }
+      ]
+    }
   },
   "reftest_nodes": {},
   "rev": null,
diff --git a/tests/wpt/mozilla/tests/css/class-namespaces-ref.html b/tests/wpt/mozilla/tests/css/class-namespaces-ref.html
new file mode 100644
index 00000000000..96c68eff366
--- /dev/null
+++ b/tests/wpt/mozilla/tests/css/class-namespaces-ref.html
@@ -0,0 +1,5 @@
+<style>
+p { background: green; }
+</style>
+<body>
+<p>AAA</p><p>BBB</p>
diff --git a/tests/wpt/mozilla/tests/css/class-namespaces.html b/tests/wpt/mozilla/tests/css/class-namespaces.html
new file mode 100644
index 00000000000..239d1629fc3
--- /dev/null
+++ b/tests/wpt/mozilla/tests/css/class-namespaces.html
@@ -0,0 +1,16 @@
+<link rel=match href=class-namespaces-ref.html>
+<style>
+.foo { background: green; }
+</style>
+<body>
+<script>
+var p = document.body.appendChild(document.createElement("p"));
+p.setAttributeNS("foo", "class", "bar");
+p.setAttributeNS("", "class", "foo");
+p.textContent = "AAA";
+
+var p = document.body.appendChild(document.createElement("p"));
+p.setAttributeNS("", "class", "foo");
+p.setAttributeNS("foo", "class", "bar");
+p.textContent = "BBB";
+</script>