diff --git a/Userland/Libraries/LibWeb/DOM/Document.h b/Userland/Libraries/LibWeb/DOM/Document.h
index 143ae6908d..640a42a51e 100644
--- a/Userland/Libraries/LibWeb/DOM/Document.h
+++ b/Userland/Libraries/LibWeb/DOM/Document.h
@@ -353,7 +353,7 @@ private:
     explicit Document(const AK::URL&);
 
     // ^HTML::GlobalEventHandlers
-    virtual EventTarget& global_event_handlers_to_event_target() final { return *this; }
+    virtual EventTarget& global_event_handlers_to_event_target(FlyString const&) final { return *this; }
 
     void tear_down_layout_tree();
 
diff --git a/Userland/Libraries/LibWeb/DOM/EventTarget.cpp b/Userland/Libraries/LibWeb/DOM/EventTarget.cpp
index a995a360b0..b56a23498a 100644
--- a/Userland/Libraries/LibWeb/DOM/EventTarget.cpp
+++ b/Userland/Libraries/LibWeb/DOM/EventTarget.cpp
@@ -218,7 +218,7 @@ ExceptionOr<bool> EventTarget::dispatch_event_binding(NonnullRefPtr<Event> event
 }
 
 // https://html.spec.whatwg.org/multipage/webappapis.html#window-reflecting-body-element-event-handler-set
-static bool is_window_reflecting_body_element_event_handler(FlyString const& name)
+bool is_window_reflecting_body_element_event_handler(FlyString const& name)
 {
     return name.is_one_of(
         HTML::EventNames::blur,
diff --git a/Userland/Libraries/LibWeb/DOM/EventTarget.h b/Userland/Libraries/LibWeb/DOM/EventTarget.h
index c0098efc47..3cef8cd7f3 100644
--- a/Userland/Libraries/LibWeb/DOM/EventTarget.h
+++ b/Userland/Libraries/LibWeb/DOM/EventTarget.h
@@ -86,4 +86,6 @@ private:
     JS::ThrowCompletionOr<void> process_event_handler_for_event(FlyString const& name, Event& event);
 };
 
+bool is_window_reflecting_body_element_event_handler(FlyString const& name);
+
 }
diff --git a/Userland/Libraries/LibWeb/HTML/GlobalEventHandlers.cpp b/Userland/Libraries/LibWeb/HTML/GlobalEventHandlers.cpp
index 78e72e7d90..c45a016023 100644
--- a/Userland/Libraries/LibWeb/HTML/GlobalEventHandlers.cpp
+++ b/Userland/Libraries/LibWeb/HTML/GlobalEventHandlers.cpp
@@ -16,14 +16,14 @@
 namespace Web::HTML {
 
 #undef __ENUMERATE
-#define __ENUMERATE(attribute_name, event_name)                                                       \
-    void GlobalEventHandlers::set_##attribute_name(Optional<Bindings::CallbackType> value)            \
-    {                                                                                                 \
-        global_event_handlers_to_event_target().set_event_handler_attribute(event_name, move(value)); \
-    }                                                                                                 \
-    Bindings::CallbackType* GlobalEventHandlers::attribute_name()                                     \
-    {                                                                                                 \
-        return global_event_handlers_to_event_target().event_handler_attribute(event_name);           \
+#define __ENUMERATE(attribute_name, event_name)                                                                 \
+    void GlobalEventHandlers::set_##attribute_name(Optional<Bindings::CallbackType> value)                      \
+    {                                                                                                           \
+        global_event_handlers_to_event_target(event_name).set_event_handler_attribute(event_name, move(value)); \
+    }                                                                                                           \
+    Bindings::CallbackType* GlobalEventHandlers::attribute_name()                                               \
+    {                                                                                                           \
+        return global_event_handlers_to_event_target(event_name).event_handler_attribute(event_name);           \
     }
 ENUMERATE_GLOBAL_EVENT_HANDLERS(__ENUMERATE)
 #undef __ENUMERATE
diff --git a/Userland/Libraries/LibWeb/HTML/GlobalEventHandlers.h b/Userland/Libraries/LibWeb/HTML/GlobalEventHandlers.h
index 7fad45cc29..facdc97a23 100644
--- a/Userland/Libraries/LibWeb/HTML/GlobalEventHandlers.h
+++ b/Userland/Libraries/LibWeb/HTML/GlobalEventHandlers.h
@@ -91,7 +91,7 @@ public:
 #undef __ENUMERATE
 
 protected:
-    virtual DOM::EventTarget& global_event_handlers_to_event_target() = 0;
+    virtual DOM::EventTarget& global_event_handlers_to_event_target(FlyString const& event_name) = 0;
 };
 
 }
diff --git a/Userland/Libraries/LibWeb/HTML/HTMLBodyElement.cpp b/Userland/Libraries/LibWeb/HTML/HTMLBodyElement.cpp
index ad0d688c6f..b3b64a6625 100644
--- a/Userland/Libraries/LibWeb/HTML/HTMLBodyElement.cpp
+++ b/Userland/Libraries/LibWeb/HTML/HTMLBodyElement.cpp
@@ -57,10 +57,14 @@ void HTMLBodyElement::parse_attribute(FlyString const& name, String const& value
     }
 }
 
-DOM::EventTarget& HTMLBodyElement::global_event_handlers_to_event_target()
+DOM::EventTarget& HTMLBodyElement::global_event_handlers_to_event_target(FlyString const& event_name)
 {
     // NOTE: This is a little weird, but IIUC document.body.onload actually refers to window.onload
-    return document().window();
+    // NOTE: document.body can return either a HTMLBodyElement or HTMLFrameSetElement, so both these elements must support this mapping.
+    if (DOM::is_window_reflecting_body_element_event_handler(event_name))
+        return document().window();
+
+    return *this;
 }
 
 }
diff --git a/Userland/Libraries/LibWeb/HTML/HTMLBodyElement.h b/Userland/Libraries/LibWeb/HTML/HTMLBodyElement.h
index 2aef6df4d5..21e9b3a2ef 100644
--- a/Userland/Libraries/LibWeb/HTML/HTMLBodyElement.h
+++ b/Userland/Libraries/LibWeb/HTML/HTMLBodyElement.h
@@ -22,7 +22,7 @@ public:
 
 private:
     // ^HTML::GlobalEventHandlers
-    virtual EventTarget& global_event_handlers_to_event_target() override;
+    virtual EventTarget& global_event_handlers_to_event_target(FlyString const& event_name) override;
 
     RefPtr<CSS::ImageStyleValue> m_background_style_value;
 };
diff --git a/Userland/Libraries/LibWeb/HTML/HTMLElement.h b/Userland/Libraries/LibWeb/HTML/HTMLElement.h
index c4f0ba8bfc..694a3630bc 100644
--- a/Userland/Libraries/LibWeb/HTML/HTMLElement.h
+++ b/Userland/Libraries/LibWeb/HTML/HTMLElement.h
@@ -54,7 +54,7 @@ protected:
 
 private:
     // ^HTML::GlobalEventHandlers
-    virtual DOM::EventTarget& global_event_handlers_to_event_target() override { return *this; }
+    virtual DOM::EventTarget& global_event_handlers_to_event_target(FlyString const&) override { return *this; }
 
     enum class ContentEditableState {
         True,
diff --git a/Userland/Libraries/LibWeb/HTML/HTMLFrameSetElement.cpp b/Userland/Libraries/LibWeb/HTML/HTMLFrameSetElement.cpp
index 7e793918b6..50aa75edf9 100644
--- a/Userland/Libraries/LibWeb/HTML/HTMLFrameSetElement.cpp
+++ b/Userland/Libraries/LibWeb/HTML/HTMLFrameSetElement.cpp
@@ -14,4 +14,15 @@ HTMLFrameSetElement::HTMLFrameSetElement(DOM::Document& document, DOM::Qualified
 }
 
 HTMLFrameSetElement::~HTMLFrameSetElement() = default;
+
+DOM::EventTarget& HTMLFrameSetElement::global_event_handlers_to_event_target(FlyString const& event_name)
+{
+    // NOTE: This is a little weird, but IIUC document.body.onload actually refers to window.onload
+    // NOTE: document.body can return either a HTMLBodyElement or HTMLFrameSetElement, so both these elements must support this mapping.
+    if (DOM::is_window_reflecting_body_element_event_handler(event_name))
+        return document().window();
+
+    return *this;
+}
+
 }
diff --git a/Userland/Libraries/LibWeb/HTML/HTMLFrameSetElement.h b/Userland/Libraries/LibWeb/HTML/HTMLFrameSetElement.h
index 998bb60637..e6170a5607 100644
--- a/Userland/Libraries/LibWeb/HTML/HTMLFrameSetElement.h
+++ b/Userland/Libraries/LibWeb/HTML/HTMLFrameSetElement.h
@@ -17,6 +17,10 @@ public:
 
     HTMLFrameSetElement(DOM::Document&, DOM::QualifiedName);
     virtual ~HTMLFrameSetElement() override;
+
+private:
+    // ^HTML::GlobalEventHandlers
+    virtual EventTarget& global_event_handlers_to_event_target(FlyString const& event_name) override;
 };
 
 }
diff --git a/Userland/Libraries/LibWeb/HTML/Window.h b/Userland/Libraries/LibWeb/HTML/Window.h
index 52aa16fe03..df4b56fa9b 100644
--- a/Userland/Libraries/LibWeb/HTML/Window.h
+++ b/Userland/Libraries/LibWeb/HTML/Window.h
@@ -128,7 +128,7 @@ private:
     explicit Window(DOM::Document&);
 
     // ^HTML::GlobalEventHandlers
-    virtual DOM::EventTarget& global_event_handlers_to_event_target() override { return *this; }
+    virtual DOM::EventTarget& global_event_handlers_to_event_target(FlyString const&) override { return *this; }
 
     enum class Repeat {
         Yes,