diff --git a/Userland/Libraries/LibWeb/Bindings/MainThreadVM.cpp b/Userland/Libraries/LibWeb/Bindings/MainThreadVM.cpp
index 91c269c46cd..69658f73123 100644
--- a/Userland/Libraries/LibWeb/Bindings/MainThreadVM.cpp
+++ b/Userland/Libraries/LibWeb/Bindings/MainThreadVM.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2021-2022, Andreas Kling <kling@serenityos.org>
  * Copyright (c) 2021, Luke Wilde <lukew@serenityos.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
@@ -307,12 +307,27 @@ JS::VM& main_thread_vm()
         // NOTE: We push a dummy execution context onto the JS execution context stack,
         //       just to make sure that it's never empty.
         auto& custom_data = *verify_cast<WebEngineCustomData>(vm->custom_data());
-        custom_data.root_execution_context = make<JS::ExecutionContext>(vm->heap());
+        custom_data.root_execution_context = MUST(JS::Realm::initialize_host_defined_realm(
+            *vm, [&](JS::Realm& realm) -> JS::GlobalObject* {
+                auto internal_window = HTML::Window::create();
+                custom_data.internal_window_object = JS::make_handle(vm->heap().allocate<Bindings::WindowObject>(realm, realm, internal_window));
+                return custom_data.internal_window_object.cell(); },
+            [](JS::Realm&) -> JS::GlobalObject* {
+                return nullptr;
+            }));
+
         vm->push_execution_context(*custom_data.root_execution_context);
     }
     return *vm;
 }
 
+Bindings::WindowObject& main_thread_internal_window_object()
+{
+    auto& vm = main_thread_vm();
+    auto& custom_data = verify_cast<WebEngineCustomData>(*vm.custom_data());
+    return *custom_data.internal_window_object;
+}
+
 // https://dom.spec.whatwg.org/#queue-a-mutation-observer-compound-microtask
 void queue_mutation_observer_microtask(DOM::Document& document)
 {
diff --git a/Userland/Libraries/LibWeb/Bindings/MainThreadVM.h b/Userland/Libraries/LibWeb/Bindings/MainThreadVM.h
index 83a15a414de..88a473e7713 100644
--- a/Userland/Libraries/LibWeb/Bindings/MainThreadVM.h
+++ b/Userland/Libraries/LibWeb/Bindings/MainThreadVM.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2021-2022, Andreas Kling <kling@serenityos.org>
  * Copyright (c) 2021, Luke Wilde <lukew@serenityos.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
@@ -11,6 +11,7 @@
 #include <LibJS/Forward.h>
 #include <LibJS/Runtime/JobCallback.h>
 #include <LibJS/Runtime/VM.h>
+#include <LibWeb/Bindings/WindowObject.h>
 #include <LibWeb/DOM/MutationObserver.h>
 #include <LibWeb/HTML/EventLoop/EventLoop.h>
 
@@ -31,6 +32,10 @@ struct WebEngineCustomData final : public JS::VM::CustomData {
     NonnullRefPtrVector<DOM::MutationObserver> mutation_observers;
 
     OwnPtr<JS::ExecutionContext> root_execution_context;
+
+    // This object is used as the global object for GC-allocated objects that don't
+    // belong to a web-facing global object.
+    JS::Handle<Bindings::WindowObject> internal_window_object;
 };
 
 struct WebEngineCustomJobCallbackData final : public JS::JobCallback::CustomData {
@@ -48,6 +53,7 @@ struct WebEngineCustomJobCallbackData final : public JS::JobCallback::CustomData
 
 HTML::ClassicScript* active_script();
 JS::VM& main_thread_vm();
+Bindings::WindowObject& main_thread_internal_window_object();
 void queue_mutation_observer_microtask(DOM::Document&);
 NonnullOwnPtr<JS::ExecutionContext> create_a_new_javascript_realm(JS::VM&, Function<JS::GlobalObject*(JS::Realm&)> create_global_object, Function<JS::GlobalObject*(JS::Realm&)> create_global_this_value);