diff --git a/Libraries/LibWeb/HTML/CustomElements/CustomElementRegistry.cpp b/Libraries/LibWeb/HTML/CustomElements/CustomElementRegistry.cpp
index c5e0ea656e4..20a552439ad 100644
--- a/Libraries/LibWeb/HTML/CustomElements/CustomElementRegistry.cpp
+++ b/Libraries/LibWeb/HTML/CustomElements/CustomElementRegistry.cpp
@@ -326,7 +326,7 @@ JS::ThrowCompletionOr<void> CustomElementRegistry::define(String const& name, We
 }
 
 // https://html.spec.whatwg.org/multipage/custom-elements.html#dom-customelementregistry-get
-Variant<GC::Root<WebIDL::CallbackType>, JS::Value> CustomElementRegistry::get(String const& name) const
+Variant<GC::Root<WebIDL::CallbackType>, Empty> CustomElementRegistry::get(String const& name) const
 {
     // 1. If this's custom element definition set contains an item with name name, then return that item's constructor.
     auto existing_definition_iterator = m_custom_element_definitions.find_if([&name](auto const& definition) {
@@ -337,7 +337,7 @@ Variant<GC::Root<WebIDL::CallbackType>, JS::Value> CustomElementRegistry::get(St
         return GC::make_root((*existing_definition_iterator)->constructor());
 
     // 2. Return undefined.
-    return JS::js_undefined();
+    return Empty {};
 }
 
 // https://html.spec.whatwg.org/multipage/custom-elements.html#dom-customelementregistry-getname
diff --git a/Libraries/LibWeb/HTML/CustomElements/CustomElementRegistry.h b/Libraries/LibWeb/HTML/CustomElements/CustomElementRegistry.h
index 464229ba79d..c9ab78b35ca 100644
--- a/Libraries/LibWeb/HTML/CustomElements/CustomElementRegistry.h
+++ b/Libraries/LibWeb/HTML/CustomElements/CustomElementRegistry.h
@@ -25,7 +25,7 @@ public:
     virtual ~CustomElementRegistry() override;
 
     JS::ThrowCompletionOr<void> define(String const& name, WebIDL::CallbackType* constructor, ElementDefinitionOptions options);
-    Variant<GC::Root<WebIDL::CallbackType>, JS::Value> get(String const& name) const;
+    Variant<GC::Root<WebIDL::CallbackType>, Empty> get(String const& name) const;
     Optional<String> get_name(GC::Root<WebIDL::CallbackType> const& constructor) const;
     WebIDL::ExceptionOr<GC::Ref<WebIDL::Promise>> when_defined(String const& name);
     void upgrade(GC::Ref<DOM::Node> root) const;
diff --git a/Libraries/LibWeb/HTML/Window.cpp b/Libraries/LibWeb/HTML/Window.cpp
index c5013fe60fc..850a5a8c80f 100644
--- a/Libraries/LibWeb/HTML/Window.cpp
+++ b/Libraries/LibWeb/HTML/Window.cpp
@@ -1199,12 +1199,12 @@ WebIDL::ExceptionOr<void> Window::post_message(JS::Value message, String const&
 }
 
 // https://dom.spec.whatwg.org/#dom-window-event
-Variant<GC::Root<DOM::Event>, JS::Value> Window::event() const
+Variant<GC::Root<DOM::Event>, Empty> Window::event() const
 {
     // The event getter steps are to return this’s current event.
     if (auto* current_event = this->current_event())
         return make_root(const_cast<DOM::Event&>(*current_event));
-    return JS::js_undefined();
+    return Empty {};
 }
 
 // https://w3c.github.io/csswg-drafts/cssom/#dom-window-getcomputedstyle
diff --git a/Libraries/LibWeb/HTML/Window.h b/Libraries/LibWeb/HTML/Window.h
index 32d85912aa9..87f36ba038b 100644
--- a/Libraries/LibWeb/HTML/Window.h
+++ b/Libraries/LibWeb/HTML/Window.h
@@ -196,7 +196,7 @@ public:
     WebIDL::ExceptionOr<void> post_message(JS::Value message, String const&, Vector<GC::Root<JS::Object>> const&);
     WebIDL::ExceptionOr<void> post_message(JS::Value message, WindowPostMessageOptions const&);
 
-    Variant<GC::Root<DOM::Event>, JS::Value> event() const;
+    Variant<GC::Root<DOM::Event>, Empty> event() const;
 
     [[nodiscard]] GC::Ref<CSS::CSSStyleDeclaration> get_computed_style(DOM::Element&, Optional<String> const& pseudo_element) const;
 
diff --git a/Meta/Lagom/Tools/CodeGenerators/LibWeb/BindingsGenerator/IDLGenerators.cpp b/Meta/Lagom/Tools/CodeGenerators/LibWeb/BindingsGenerator/IDLGenerators.cpp
index 07332287523..d36203836cb 100644
--- a/Meta/Lagom/Tools/CodeGenerators/LibWeb/BindingsGenerator/IDLGenerators.cpp
+++ b/Meta/Lagom/Tools/CodeGenerators/LibWeb/BindingsGenerator/IDLGenerators.cpp
@@ -231,9 +231,15 @@ CppType idl_type_name_to_cpp_type(Type const& type, Interface const& interface)
     if (type.name() == "long" && !type.is_nullable())
         return { .name = "WebIDL::Long", .sequence_storage_type = SequenceStorageType::Vector };
 
-    if (type.name() == "any" || type.name() == "undefined")
+    if (type.name() == "any")
         return { .name = "JS::Value", .sequence_storage_type = SequenceStorageType::RootVector };
 
+    // NOTE: undefined is a somewhat special case that may be used in a union to represent the javascript 'undefined' (and
+    //       only ever js_undefined). Therefore, we say that the type is Empty here, so that a union of (T, undefined) is
+    //       generated as Variant<T, Empty>, which is then returned in the Variant's visit as undefined if it is Empty.
+    if (type.name() == "undefined")
+        return { .name = "Empty", .sequence_storage_type = SequenceStorageType::RootVector };
+
     if (type.name() == "object")
         return { .name = "GC::Root<JS::Object>", .sequence_storage_type = SequenceStorageType::Vector };