diff --git a/source b/source
index eb7730afdb1..e15ee45197d 100644
--- a/source
+++ b/source
@@ -92834,6 +92834,16 @@ interface <dfn interface>BeforeUnloadEvent</dfn> : <span>Event</span> {
     involved.</p>
    </dd>
 
+   <dt>A <dfn id="concept-environment-top-level-site" export
+   for="environment">top-level site</dfn></dt>
+   <dd><p>A <span>site</span> <span data-x="obtain a site">obtained</span> from the "top-level"
+   <span>environment settings object</span>'s
+   <span data-x="concept-settings-object-origin">origin</span>.  For a "top-level" potential
+   execution environment it is set to the site of the
+   <span data-x="concept-environment-creation-url">creation url</span>.  For a worker it is set to
+   the top-level site of its creator.</p>
+   </dd>
+
    <dt>A <dfn data-x="concept-environment-target-browsing-context" export
    for="environment">target browsing context</dfn></dt>
    <dd><p>Null or a target <span>browsing context</span> for a <span