diff --git a/css-animations-2/Overview.bs b/css-animations-2/Overview.bs
index 81573af9a92a..76eab389af49 100644
--- a/css-animations-2/Overview.bs
+++ b/css-animations-2/Overview.bs
@@ -878,6 +878,33 @@ expressed in milliseconds, it must be divided by 1,000 to produce a value in
 seconds before being assigned to the {{AnimationEvent/elapsedTime}} member of
 the {{AnimationEvent}}.
 
+## The <code>AnimationEvent</code> Interface ## {#interface-animationevent}
+
+### IDL Definition ### {#interface-animationevent-idl}
+
+Add {{AnimationEvent/animation}} to the {{AnimationEvent}} interface and {{AnimationEventInit}} dictionary as follows:
+
+<pre class="idl">
+[Exposed=Window]
+partial interface AnimationEvent {
+  readonly attribute CSSAnimation? animation;
+};
+
+partial dictionary AnimationEventInit {
+  CSSAnimation? animation = null;
+};
+</pre>
+
+### Attributes ### {#interface-animationevent-attributes}
+
+Add attribute descriptions as follows:
+
+<dl dfn-type=attribute dfn-for=AnimationEvent>
+  <dt><dfn>animation</dfn>
+  <dd>
+    The CSS Animation that fired the event.
+</dl>
+
 # DOM Interfaces # {#interface-dom}
 
 ## The CSSAnimation interface ## {#the-CSSAnimation-interface}
diff --git a/css-transitions-2/Overview.bs b/css-transitions-2/Overview.bs
index d4718f7b4548..29793811610a 100644
--- a/css-transitions-2/Overview.bs
+++ b/css-transitions-2/Overview.bs
@@ -582,6 +582,30 @@ the {{TransitionEvent}}.
 
 </div>
 
+## Interface {{TransitionEvent}} ## {#interface-transitionevent}
+
+Add animation to the {{TransitionEvent}} interface and {{TransitionEventInit}} dictionary as follows:
+
+### IDL Definition ### {#interface-transitionevent-idl}
+
+<pre class="idl">
+[Exposed=Window]
+partial interface TransitionEvent {
+  readonly attribute CSSTransition? animation;
+};
+
+partial dictionary TransitionEventInit {
+  CSSTransition? animation = null;
+};
+</pre>
+
+### Attributes ### {#interface-transitionevent-attributes}
+
+Add attribute descriptions as follows:
+
+:   <code class='attribute-name'><dfn attribute for="TransitionEvent" id="Events-TransitionEvent-animation">animation</dfn></code>
+::  The CSS Transition corresponding to the transition that fired the event.
+
 # DOM Interfaces # {#interface-dom}
 
 ## The CSSTransition interface ## {#the-CSSTransition-interface}