diff --git a/Userland/Libraries/LibWeb/DOM/Document.cpp b/Userland/Libraries/LibWeb/DOM/Document.cpp
index f072283a75..46dd53bba0 100644
--- a/Userland/Libraries/LibWeb/DOM/Document.cpp
+++ b/Userland/Libraries/LibWeb/DOM/Document.cpp
@@ -1116,8 +1116,7 @@ void Document::adopt_node(Node& node)
         node.remove();
 
     if (&old_document != this) {
-        // FIXME: This should be shadow-including.
-        node.for_each_in_inclusive_subtree([&](auto& inclusive_descendant) {
+        node.for_each_shadow_including_descendant([&](auto& inclusive_descendant) {
             inclusive_descendant.set_document({}, *this);
             // FIXME: If inclusiveDescendant is an element, then set the node document of each attribute in inclusiveDescendant’s attribute list to document.
             return IterationDecision::Continue;
@@ -1127,8 +1126,7 @@ void Document::adopt_node(Node& node)
         //        enqueue a custom element callback reaction with inclusiveDescendant, callback name "adoptedCallback",
         //        and an argument list containing oldDocument and document.
 
-        // FIXME: This should be shadow-including.
-        node.for_each_in_inclusive_subtree([&](auto& inclusive_descendant) {
+        node.for_each_shadow_including_descendant([&](auto& inclusive_descendant) {
             inclusive_descendant.adopted_from(old_document);
             return IterationDecision::Continue;
         });
diff --git a/Userland/Libraries/LibWeb/DOM/Node.h b/Userland/Libraries/LibWeb/DOM/Node.h
index d30275ef5c..8cd3ffb2c9 100644
--- a/Userland/Libraries/LibWeb/DOM/Node.h
+++ b/Userland/Libraries/LibWeb/DOM/Node.h
@@ -231,6 +231,10 @@ public:
 
     void queue_mutation_record(FlyString const& type, String attribute_name, String attribute_namespace, String old_value, NonnullRefPtr<NodeList> added_nodes, NonnullRefPtr<NodeList> removed_nodes, Node* previous_sibling, Node* next_sibling);
 
+    // https://dom.spec.whatwg.org/#concept-shadow-including-descendant
+    template<typename Callback>
+    IterationDecision for_each_shadow_including_descendant(Callback);
+
 protected:
     Node(Document&, NodeType);
 
diff --git a/Userland/Libraries/LibWeb/DOM/ShadowRoot.h b/Userland/Libraries/LibWeb/DOM/ShadowRoot.h
index b4306c4461..ea561e7b4c 100644
--- a/Userland/Libraries/LibWeb/DOM/ShadowRoot.h
+++ b/Userland/Libraries/LibWeb/DOM/ShadowRoot.h
@@ -45,4 +45,22 @@ private:
 template<>
 inline bool Node::fast_is<ShadowRoot>() const { return is_shadow_root(); }
 
+template<typename Callback>
+inline IterationDecision Node::for_each_shadow_including_descendant(Callback callback)
+{
+    if (callback(*this) == IterationDecision::Break)
+        return IterationDecision::Break;
+    for (auto* child = first_child(); child; child = child->next_sibling()) {
+        if (child->is_element()) {
+            if (RefPtr<ShadowRoot> shadow_root = static_cast<Element*>(child)->shadow_root()) {
+                if (shadow_root->for_each_shadow_including_descendant(callback) == IterationDecision::Break)
+                    return IterationDecision::Break;
+            }
+        }
+        if (child->for_each_shadow_including_descendant(callback) == IterationDecision::Break)
+            return IterationDecision::Break;
+    }
+    return IterationDecision::Continue;
+}
+
 }