diff --git a/Userland/Libraries/LibWeb/DOM/Node.h b/Userland/Libraries/LibWeb/DOM/Node.h
index 02d59dc6fb..4af2f3f720 100644
--- a/Userland/Libraries/LibWeb/DOM/Node.h
+++ b/Userland/Libraries/LibWeb/DOM/Node.h
@@ -72,6 +72,7 @@ public:
     bool is_parent_node() const { return is_element() || is_document() || is_document_fragment(); }
     bool is_slottable() const { return is_element() || is_text(); }
     bool is_attribute() const { return type() == NodeType::ATTRIBUTE_NODE; }
+    virtual bool is_shadow_root() const { return false; }
 
     virtual bool requires_svg_container() const { return false; }
     virtual bool is_svg_container() const { return false; }
diff --git a/Userland/Libraries/LibWeb/DOM/ShadowRoot.h b/Userland/Libraries/LibWeb/DOM/ShadowRoot.h
index 7ea5ca32ff..f550c0e5cb 100644
--- a/Userland/Libraries/LibWeb/DOM/ShadowRoot.h
+++ b/Userland/Libraries/LibWeb/DOM/ShadowRoot.h
@@ -34,6 +34,7 @@ public:
 private:
     // ^Node
     virtual FlyString node_name() const override { return "#shadow-root"; }
+    virtual bool is_shadow_root() const final { return true; }
 
     // NOTE: The specification doesn't seem to specify a default value for closed. Assuming false for now.
     bool m_closed { false };
@@ -41,4 +42,7 @@ private:
     bool m_available_to_element_internals { false };
 };
 
+template<>
+inline bool Node::fast_is<ShadowRoot>() const { return is_shadow_root(); }
+
 }
diff --git a/Userland/Libraries/LibWeb/Layout/ListItemMarkerBox.h b/Userland/Libraries/LibWeb/Layout/ListItemMarkerBox.h
index 3a9343e8b2..e9b31876d5 100644
--- a/Userland/Libraries/LibWeb/Layout/ListItemMarkerBox.h
+++ b/Userland/Libraries/LibWeb/Layout/ListItemMarkerBox.h
@@ -24,6 +24,7 @@ public:
     CSS::ListStyleType list_style_type() const { return m_list_style_type; }
 
 private:
+    virtual bool is_list_item_marker_box() const final { return true; }
     virtual bool can_have_children() const override { return false; }
 
     CSS::ListStyleType m_list_style_type { CSS::ListStyleType::None };
@@ -32,4 +33,7 @@ private:
     String m_text {};
 };
 
+template<>
+inline bool Node::fast_is<ListItemMarkerBox>() const { return is_list_item_marker_box(); }
+
 }
diff --git a/Userland/Libraries/LibWeb/Layout/Node.h b/Userland/Libraries/LibWeb/Layout/Node.h
index f65f263142..46cedbd06f 100644
--- a/Userland/Libraries/LibWeb/Layout/Node.h
+++ b/Userland/Libraries/LibWeb/Layout/Node.h
@@ -74,6 +74,8 @@ public:
     virtual bool is_svg_box() const { return false; }
     virtual bool is_svg_geometry_box() const { return false; }
     virtual bool is_label() const { return false; }
+    virtual bool is_replaced_box() const { return false; }
+    virtual bool is_list_item_marker_box() const { return false; }
 
     template<typename T>
     bool fast_is() const = delete;
diff --git a/Userland/Libraries/LibWeb/Layout/ReplacedBox.h b/Userland/Libraries/LibWeb/Layout/ReplacedBox.h
index 55b8afc370..28032d5aa8 100644
--- a/Userland/Libraries/LibWeb/Layout/ReplacedBox.h
+++ b/Userland/Libraries/LibWeb/Layout/ReplacedBox.h
@@ -32,9 +32,14 @@ public:
     virtual bool can_have_children() const override { return false; }
 
 private:
+    virtual bool is_replaced_box() const final { return true; }
+
     Optional<float> m_intrinsic_width;
     Optional<float> m_intrinsic_height;
     Optional<float> m_intrinsic_aspect_ratio;
 };
 
+template<>
+inline bool Node::fast_is<ReplacedBox>() const { return is_replaced_box(); }
+
 }