diff --git a/src/components/script/dom/attr.rs b/src/components/script/dom/attr.rs
index dd289ff3b88..237806c07f8 100644
--- a/src/components/script/dom/attr.rs
+++ b/src/components/script/dom/attr.rs
@@ -14,6 +14,11 @@ use servo_util::namespace;
 use servo_util::namespace::Namespace;
 use servo_util::str::DOMString;
 
+pub enum AttrSettingType {
+    FirstSetAttr,
+    ReplacedAttr,
+}
+
 #[deriving(Encodable)]
 pub struct Attr {
     reflector_: Reflector,
@@ -59,12 +64,17 @@ impl Attr {
         reflect_dom_object(~attr, window, AttrBinding::Wrap)
     }
 
-    pub fn set_value(&mut self, value: DOMString) {
+    pub fn set_value(&mut self, set_type: AttrSettingType, value: DOMString) {
         let node: JS<Node> = NodeCast::from(&self.owner);
         let namespace_is_null = self.namespace == namespace::Null;
 
-        if namespace_is_null {
-            vtable_for(&node).before_remove_attr(self.local_name.clone(), self.value.clone());
+        match set_type {
+            ReplacedAttr => {
+                if namespace_is_null {
+                    vtable_for(&node).before_remove_attr(self.local_name.clone(), self.value.clone());
+                }
+            }
+            FirstSetAttr => {}
         }
 
         self.value = value;
@@ -89,7 +99,7 @@ impl Attr {
     }
 
     pub fn SetValue(&mut self, value: DOMString) {
-        self.set_value(value);
+        self.set_value(ReplacedAttr, value);
     }
 
     pub fn Name(&self) -> DOMString {
diff --git a/src/components/script/dom/element.rs b/src/components/script/dom/element.rs
index 2796b7aa870..d60181f5349 100644
--- a/src/components/script/dom/element.rs
+++ b/src/components/script/dom/element.rs
@@ -4,7 +4,7 @@
 
 //! Element nodes.
 
-use dom::attr::Attr;
+use dom::attr::{Attr, AttrSettingType, ReplacedAttr, FirstSetAttr};
 use dom::attrlist::AttrList;
 use dom::bindings::codegen::ElementBinding;
 use dom::bindings::codegen::InheritTypes::{ElementDerived, NodeCast};
@@ -263,23 +263,22 @@ impl AttributeHandlers for JS<Element> {
                         prefix: Option<DOMString>, cb: |&JS<Attr>| -> bool) {
         let node: JS<Node> = NodeCast::from(self);
         let idx = self.get().attrs.iter().position(cb);
-        match idx {
+        let (mut attr, set_type): (JS<Attr>, AttrSettingType) = match idx {
             Some(idx) => {
-                self.get_mut().attrs[idx].get_mut().set_value(value.clone());
+                let attr = self.get_mut().attrs[idx].clone();
+                (attr, ReplacedAttr)
             }
 
             None => {
                 let doc = node.get().owner_doc().get();
-                let new_attr = Attr::new(&doc.window, local_name.clone(), value.clone(),
+                let attr = Attr::new(&doc.window, local_name.clone(), value.clone(),
                                          name, namespace.clone(), prefix, self.clone());
-                self.get_mut().attrs.push(new_attr);
-
-                // FIXME: This part should be handled in `Attr`.
-                if namespace == namespace::Null {
-                    vtable_for(&node).after_set_attr(local_name, value);
-                }
+                self.get_mut().attrs.push(attr.clone());
+                (attr, FirstSetAttr)
             }
-        }
+        };
+
+        attr.get_mut().set_value(set_type, value);
     }
 
     // http://dom.spec.whatwg.org/#dom-element-setattribute