diff --git a/source b/source
index 38926c6a294..da23f63f0a0 100644
--- a/source
+++ b/source
@@ -81753,6 +81753,11 @@ State: <OUTPUT NAME=I>1</OUTPUT> <INPUT VALUE="Increment" TYPE=BUTTON O
    data-x="concept-location-ancestor-origins-list">ancestor origins list</span>.</p></li>
   </ol>
 
+  <p class="warning">The details of how the <code
+  data-x="dom-location-ancestorOrigins">ancestorOrigins</code> works are still controversial and are
+  expected to change. See <a href="https://github.com/whatwg/html/issues/1918">issue #1918</a> for
+  more information.</p>
+
   <hr>
 
   <p id="location-internal-methods">As explained earlier, the <code>Location</code> exotic object