diff --git a/Userland/Libraries/LibWeb/DOM/Event.h b/Userland/Libraries/LibWeb/DOM/Event.h
index eeb9784c4fd..f9cc2f74e61 100644
--- a/Userland/Libraries/LibWeb/DOM/Event.h
+++ b/Userland/Libraries/LibWeb/DOM/Event.h
@@ -144,6 +144,11 @@ public:
 
     Vector<JS::Handle<EventTarget>> composed_path() const;
 
+    template<typename T>
+    bool fast_is() const = delete;
+
+    virtual bool is_mouse_event() const { return false; }
+
 protected:
     void initialize_event(String const&, bool, bool);
 
diff --git a/Userland/Libraries/LibWeb/UIEvents/MouseEvent.h b/Userland/Libraries/LibWeb/UIEvents/MouseEvent.h
index a27d85ffe20..69b8d085290 100644
--- a/Userland/Libraries/LibWeb/UIEvents/MouseEvent.h
+++ b/Userland/Libraries/LibWeb/UIEvents/MouseEvent.h
@@ -71,6 +71,8 @@ protected:
     virtual void initialize(JS::Realm&) override;
 
 private:
+    virtual bool is_mouse_event() const override { return true; }
+
     void set_event_characteristics();
 
     double m_screen_x { 0 };
@@ -102,3 +104,10 @@ private:
 };
 
 }
+
+namespace Web::DOM {
+
+template<>
+inline bool Event::fast_is<UIEvents::MouseEvent>() const { return is_mouse_event(); }
+
+}