diff --git a/Tests/LibWeb/Text/expected/HTML/Form-named-property-access.txt b/Tests/LibWeb/Text/expected/HTML/Form-named-property-access.txt
index dee9ba8cbde..3476db93e73 100644
--- a/Tests/LibWeb/Text/expected/HTML/Form-named-property-access.txt
+++ b/Tests/LibWeb/Text/expected/HTML/Form-named-property-access.txt
@@ -1,4 +1,4 @@
-                                                            == Elements and Names ==
+                                                              == Elements and Names ==
 formy.length: 12
 elements.length: 12
 elements[0] === form.foo
@@ -38,3 +38,6 @@ elements in changeForFormAttribute: 1
 elements in changeForFormAttribute: 0
 elements in changeForFormAttribute: 1
 elements in changeForFormAttribute: 0
+== Form element appears after a form-associated element ==
+elements in formAfterInput: 1
+typeof formAfterInput.inputBeforeForm: object
diff --git a/Tests/LibWeb/Text/input/HTML/Form-named-property-access.html b/Tests/LibWeb/Text/input/HTML/Form-named-property-access.html
index 8b492768e73..1f928a5ae06 100644
--- a/Tests/LibWeb/Text/input/HTML/Form-named-property-access.html
+++ b/Tests/LibWeb/Text/input/HTML/Form-named-property-access.html
@@ -63,6 +63,9 @@
 <form id="changeForFormAttribute"></form>
 <input id="changeForFormAttributeInput" type="text" name="changeForFormAttribute" />
 
+<input id="inputBeforeForm" type="text" form="formAfterInput" />
+<form id="formAfterInput"></form>
+
 <script src="../include.js"></script>
 <script>
     test(() => {
@@ -138,5 +141,10 @@
 
         changeForFormAttributeInput.removeAttribute("form");
         println(`elements in changeForFormAttribute: ${changeForFormAttribute.elements.length}`);
+
+        println("== Form element appears after a form-associated element ==");
+        let formAfterInput = document.getElementById("formAfterInput");
+        println(`elements in formAfterInput: ${formAfterInput.elements.length}`);
+        println(`typeof formAfterInput.inputBeforeForm: ${typeof formAfterInput.inputBeforeForm}`);
     });
 </script>
diff --git a/Userland/Libraries/LibWeb/DOM/Document.cpp b/Userland/Libraries/LibWeb/DOM/Document.cpp
index cc5e9e6a661..f283e0e0692 100644
--- a/Userland/Libraries/LibWeb/DOM/Document.cpp
+++ b/Userland/Libraries/LibWeb/DOM/Document.cpp
@@ -449,6 +449,9 @@ void Document::visit_edges(Cell::Visitor& visitor)
         visitor.visit(timeline);
 
     visitor.visit(m_list_of_available_images);
+
+    for (auto* form_associated_element : m_form_associated_elements_with_form_attribute)
+        visitor.visit(form_associated_element->form_associated_element_to_html_element());
 }
 
 // https://w3c.github.io/selection-api/#dom-document-getselection
@@ -3683,4 +3686,28 @@ void Document::append_pending_animation_event(Web::DOM::Document::PendingAnimati
     m_pending_animation_event_queue.append(event);
 }
 
+void Document::element_id_changed(Badge<DOM::Element>)
+{
+    for (auto* form_associated_element : m_form_associated_elements_with_form_attribute)
+        form_associated_element->element_id_changed({});
+}
+
+void Document::element_with_id_was_added_or_removed(Badge<DOM::Element>)
+{
+    for (auto* form_associated_element : m_form_associated_elements_with_form_attribute)
+        form_associated_element->element_with_id_was_added_or_removed({});
+}
+
+void Document::add_form_associated_element_with_form_attribute(HTML::FormAssociatedElement& form_associated_element)
+{
+    m_form_associated_elements_with_form_attribute.append(&form_associated_element);
+}
+
+void Document::remove_form_associated_element_with_form_attribute(HTML::FormAssociatedElement& form_associated_element)
+{
+    m_form_associated_elements_with_form_attribute.remove_all_matching([&](auto* element) {
+        return element == &form_associated_element;
+    });
+}
+
 }
diff --git a/Userland/Libraries/LibWeb/DOM/Document.h b/Userland/Libraries/LibWeb/DOM/Document.h
index 3d825472859..778ecb4b99f 100644
--- a/Userland/Libraries/LibWeb/DOM/Document.h
+++ b/Userland/Libraries/LibWeb/DOM/Document.h
@@ -554,6 +554,12 @@ public:
     JS::GCPtr<HTML::SessionHistoryEntry> latest_entry() const { return m_latest_entry; }
     void set_latest_entry(JS::GCPtr<HTML::SessionHistoryEntry> e) { m_latest_entry = e; }
 
+    void element_id_changed(Badge<DOM::Element>);
+    void element_with_id_was_added_or_removed(Badge<DOM::Element>);
+
+    void add_form_associated_element_with_form_attribute(HTML::FormAssociatedElement&);
+    void remove_form_associated_element_with_form_attribute(HTML::FormAssociatedElement&);
+
 protected:
     virtual void initialize(JS::Realm&) override;
     virtual void visit_edges(Cell::Visitor&) override;
@@ -775,6 +781,8 @@ private:
 
     // https://html.spec.whatwg.org/multipage/browsing-the-web.html#scripts-may-run-for-the-newly-created-document
     bool m_ready_to_run_scripts { false };
+
+    Vector<HTML::FormAssociatedElement*> m_form_associated_elements_with_form_attribute;
 };
 
 template<>
diff --git a/Userland/Libraries/LibWeb/DOM/Element.cpp b/Userland/Libraries/LibWeb/DOM/Element.cpp
index e129c24e96f..9bc01bccfca 100644
--- a/Userland/Libraries/LibWeb/DOM/Element.cpp
+++ b/Userland/Libraries/LibWeb/DOM/Element.cpp
@@ -465,6 +465,8 @@ void Element::attribute_changed(FlyString const& name, Optional<String> const& v
             m_id = {};
         else
             m_id = value_or_empty;
+
+        document().element_id_changed({});
     } else if (name == HTML::AttributeNames::name) {
         if (!value.has_value())
             m_name = {};
@@ -1026,6 +1028,22 @@ int Element::client_height() const
     return paintable_box()->absolute_padding_box_rect().height().to_int();
 }
 
+void Element::inserted()
+{
+    Base::inserted();
+
+    if (m_id.has_value())
+        document().element_with_id_was_added_or_removed({});
+}
+
+void Element::removed_from(Node* node)
+{
+    Base::removed_from(node);
+
+    if (m_id.has_value())
+        document().element_with_id_was_added_or_removed({});
+}
+
 void Element::children_changed()
 {
     Node::children_changed();
diff --git a/Userland/Libraries/LibWeb/DOM/Element.h b/Userland/Libraries/LibWeb/DOM/Element.h
index fa1218c52ea..6a0e1b7ccc3 100644
--- a/Userland/Libraries/LibWeb/DOM/Element.h
+++ b/Userland/Libraries/LibWeb/DOM/Element.h
@@ -375,6 +375,8 @@ protected:
     Element(Document&, DOM::QualifiedName);
     virtual void initialize(JS::Realm&) override;
 
+    virtual void inserted() override;
+    virtual void removed_from(Node*) override;
     virtual void children_changed() override;
     virtual i32 default_tab_index_value() const;
 
diff --git a/Userland/Libraries/LibWeb/HTML/FormAssociatedElement.cpp b/Userland/Libraries/LibWeb/HTML/FormAssociatedElement.cpp
index 333d424830a..7f375ba35b8 100644
--- a/Userland/Libraries/LibWeb/HTML/FormAssociatedElement.cpp
+++ b/Userland/Libraries/LibWeb/HTML/FormAssociatedElement.cpp
@@ -4,6 +4,7 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <LibWeb/DOM/Document.h>
 #include <LibWeb/HTML/FormAssociatedElement.h>
 #include <LibWeb/HTML/HTMLButtonElement.h>
 #include <LibWeb/HTML/HTMLFieldSetElement.h>
@@ -73,24 +74,45 @@ void FormAssociatedElement::form_node_was_removed()
 }
 
 // https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#association-of-controls-and-forms:category-listed-3
-void FormAssociatedElement::form_node_attribute_changed(FlyString const& name, Optional<String> const&)
+void FormAssociatedElement::form_node_attribute_changed(FlyString const& name, Optional<String> const& value)
 {
     // When a listed form-associated element's form attribute is set, changed, or removed, then the user agent must
     // reset the form owner of that element.
     if (name == HTML::AttributeNames::form) {
+        auto& html_element = form_associated_element_to_html_element();
+
+        if (value.has_value())
+            html_element.document().add_form_associated_element_with_form_attribute(*this);
+        else
+            html_element.document().remove_form_associated_element_with_form_attribute(*this);
+
         reset_form_owner();
     }
 }
 
+// https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#association-of-controls-and-forms:category-listed-4
+void FormAssociatedElement::element_id_changed(Badge<DOM::Document>)
+{
+    // When a listed form-associated element has a form attribute and the ID of any of the elements in the tree changes,
+    // then the user agent must reset the form owner of that form-associated element.
+    VERIFY(form_associated_element_to_html_element().has_attribute(HTML::AttributeNames::form));
+    reset_form_owner();
+}
+
+// https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#association-of-controls-and-forms:category-listed-5
+void FormAssociatedElement::element_with_id_was_added_or_removed(Badge<DOM::Document>)
+{
+    // When a listed form-associated element has a form attribute and an element with an ID is inserted into or removed
+    // from the Document, then the user agent must reset the form owner of that form-associated element.
+    VERIFY(form_associated_element_to_html_element().has_attribute(HTML::AttributeNames::form));
+    reset_form_owner();
+}
+
 // https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#reset-the-form-owner
 void FormAssociatedElement::reset_form_owner()
 {
     auto& html_element = form_associated_element_to_html_element();
 
-    // Although these aren't in the "reset form owner" algorithm, these here as they are triggers for this algorithm:
-    // FIXME: When a listed form-associated element has a form attribute and the ID of any of the elements in the tree changes, then the user agent must reset the form owner of that form-associated element.
-    // FIXME: When a listed form-associated element has a form attribute and an element with an ID is inserted into or removed from the Document, then the user agent must reset the form owner of that form-associated element.
-
     // 1. Unset element's parser inserted flag.
     m_parser_inserted = false;
 
diff --git a/Userland/Libraries/LibWeb/HTML/FormAssociatedElement.h b/Userland/Libraries/LibWeb/HTML/FormAssociatedElement.h
index 90a69f76106..47a33e765df 100644
--- a/Userland/Libraries/LibWeb/HTML/FormAssociatedElement.h
+++ b/Userland/Libraries/LibWeb/HTML/FormAssociatedElement.h
@@ -55,6 +55,9 @@ public:
 
     void set_form(HTMLFormElement*);
 
+    void element_id_changed(Badge<DOM::Document>);
+    void element_with_id_was_added_or_removed(Badge<DOM::Document>);
+
     bool enabled() const;
 
     void set_parser_inserted(Badge<HTMLParser>);