diff --git a/components/script/dom/css2properties.rs b/components/script/dom/css2properties.rs
index cb2a8f61a5e..9c00f596501 100644
--- a/components/script/dom/css2properties.rs
+++ b/components/script/dom/css2properties.rs
@@ -256,6 +256,9 @@ impl<'a> CSS2PropertiesMethods for JSRef<'a, CSS2Properties> {
     css_getter!(Right, "right")
     css_setter!(SetRight, "right")
 
+    css_getter!(ZIndex, "z-index")
+    css_setter!(SetZIndex, "z-index")
+
     fn IndexedGetter(self, index: u32, found: &mut bool) -> DOMString {
         let decl: JSRef<CSSStyleDeclaration> = CSSStyleDeclarationCast::from_ref(self);
         decl.IndexedGetter(index, found)
diff --git a/components/script/dom/webidls/CSS2Properties.webidl b/components/script/dom/webidls/CSS2Properties.webidl
index 603cc18dfd2..8341cce9926 100644
--- a/components/script/dom/webidls/CSS2Properties.webidl
+++ b/components/script/dom/webidls/CSS2Properties.webidl
@@ -100,4 +100,6 @@ interface CSS2Properties : CSSStyleDeclaration {
   [TreatNullAs=EmptyString] attribute DOMString width;
   [TreatNullAs=EmptyString] attribute DOMString minWidth;
   [TreatNullAs=EmptyString] attribute DOMString maxWidth;
+
+  [TreatNullAs=EmptyString] attribute DOMString zIndex;
 };