diff --git a/dom.bs b/dom.bs
index b4c0abd3..9f8c12ee 100644
--- a/dom.bs
+++ b/dom.bs
@@ -908,9 +908,16 @@ for historical reasons.
 <h3 id=interface-eventtarget>Interface {{EventTarget}}</h3>
 
 <pre class=idl>
+[Exposed=*]
+interface EventTargetInternals {
+  attribute EventTarget parent;
+}
+
+callback EventTargetCallback = undefined (EventTargetInternals internals);
+
 [Exposed=*]
 interface EventTarget {
-  constructor();
+  constructor(optional EventTargetCallback cb);
 
   undefined addEventListener(DOMString type, EventListener? callback, optional (AddEventListenerOptions or boolean) options = {});
   undefined removeEventListener(DOMString type, EventListener? callback, optional (EventListenerOptions or boolean) options = {});
@@ -939,6 +946,33 @@ when something has occurred.
 <a for=/>list</a> of zero or more <a>event listeners</a>). It is initially the empty list.
 <!-- Intentionally not exported. -->
 
+<p>Each {{EventTarget}} object has an associated <dfn for=EventTarget>attached internals</dfn> (null
+or an {{EventTargetInternals}} object), initially null.
+<!-- Intentionally not exported. -->
+
+<p>When a <dfn export for=Event id=concept-eventtarget-constructor>constructor</dfn> of the {{EventTarget}}
+interface, or of an interface that inherits from the {{EventTarget}} interface, is invoked, these steps
+must be run, given the arguments <var>eventTargetCallback</var>:
+
+<ol>
+ <li><p>Let <var>eventTarget</var> be the result of creating a new object using this interface.
+
+ <li><p>Initialize <var>eventTarget</var>'s {{EventTarget/event listener list}} attribute to the empty list.
+
+ <li><p>Initialize <var>eventTarget</var>'s {{EventTarget/parent}} attribute to null.
+
+ <li><p>Let <var>eventTargetInternals</var> a new {{EventTargetInternals}} instance.
+
+ <li><p>If <var>eventTargetCallback</var> is not null, then <a
+ for=/invoke-a-callback-function>invoke</a> <var>eventTargetCallback</var> with «
+  <var>eventTargetInternals</var> and with <var>eventTarget</var> aas the <a>callback this value</a>.
+
+ <li><p>Set <var>eventTarget</var>'s {{Eventtarget/attached internals}} attribute to
+ <var>eventTargetInternals</var>.
+
+ <li><p>Return <var>eventTarget</var>.
+</ol>
+
 <p>An <dfn export id=concept-event-listener>event listener</dfn> can be used to observe a specific
 <a>event</a> and consists of:
 
@@ -956,8 +990,9 @@ when something has occurred.
 object, an <a>event listener</a> is a broader concept as can be seen above.
 
 <p>Each {{EventTarget}} object also has an associated <dfn export>get the parent</dfn> algorithm,
-which takes an <a>event</a> <var>event</var>, and returns an {{EventTarget}} object. Unless
-specified otherwise it returns null.
+which takes an <a>event</a> <var>event</var>, and returns an {{EventTarget}}. Unless otherwise
+specified otherwise it returns the associated <a for=EventTarget>attached internals</a><a
+for=EventTargetInternals">parent</a> attribute.
 
 <p class=note><a for=/>Nodes</a>, <a for=/>shadow roots</a>, and <a>documents</a>
 override the <a>get the parent</a> algorithm.
@@ -1296,6 +1331,8 @@ property of the event being dispatched.
   <ol>
    <li><p>Let <var>touchTargets</var> be a new <a for=/>list</a>.
 
+   <li><p>Let <var>parentTargets</var> be a new <a for=/>list</a>.
+
    <li><p><a for=list>For each</a> <var>touchTarget</var> of <var>event</var>'s
    <a for=Event>touch target list</a>, <a for=list>append</a> the result of <a>retargeting</a>
    <var>touchTarget</var> against <var>target</var> to <var>touchTargets</var>.
@@ -1322,6 +1359,11 @@ property of the event being dispatched.
     <p>While <var>parent</var> is non-null:</p>
 
     <ol>
+     <li>If <var>parentTargets</var> <a for=/>contains</a> <var>parent</var> then <a>throw</a> a
+     "{{HierarchyRequestError!!exception}}" {{DOMException}}.
+
+     <li>Append <var>parent</var> to <var>parentTargets</var>.
+
      <li>
       <p>If <var>slottable</var> is non-null: