diff --git a/Userland/Libraries/LibWeb/DOM/ParentNode.h b/Userland/Libraries/LibWeb/DOM/ParentNode.h
index 1b8c3e3c5c..402c4617b3 100644
--- a/Userland/Libraries/LibWeb/DOM/ParentNode.h
+++ b/Userland/Libraries/LibWeb/DOM/ParentNode.h
@@ -41,6 +41,9 @@ protected:
     }
 };
 
+template<>
+inline bool Node::fast_is<ParentNode>() const { return is_parent_node(); }
+
 template<typename Callback>
 inline void ParentNode::for_each_child(Callback callback) const
 {