diff --git a/components/script/dom/node.rs b/components/script/dom/node.rs
index d328af22151..e628ee4b2d9 100644
--- a/components/script/dom/node.rs
+++ b/components/script/dom/node.rs
@@ -486,6 +486,7 @@ pub trait NodeHelpers<'a> {
 
     fn traverse_preorder(self) -> TreeIterator<'a>;
     fn inclusively_following_siblings(self) -> NodeSiblingIterator;
+    fn inclusively_preceding_siblings(self) -> ReverseSiblingIterator;
 
     fn to_trusted_node_address(self) -> TrustedNodeAddress;
 
@@ -754,6 +755,12 @@ impl<'a> NodeHelpers<'a> for JSRef<'a, Node> {
         }
     }
 
+    fn inclusively_preceding_siblings(self) -> ReverseSiblingIterator {
+        ReverseSiblingIterator {
+            current: Some(Temporary::from_rooted(self)),
+        }
+    }
+
     fn is_inclusive_ancestor_of(self, parent: JSRef<Node>) -> bool {
         self == parent || parent.ancestors().any(|ancestor| ancestor.root().r() == self)
     }