diff --git a/source b/source
index 4e3198ba8ee..4d72fad2f0b 100644
--- a/source
+++ b/source
@@ -87169,8 +87169,9 @@ interface <dfn interface>BeforeUnloadEvent</dfn> : <span>Event</span> {
   <span>navigable</span> <var>navigable</var> is the <span>navigable container</span> whose
   <span>nested navigable</span> is <var>navigable</var>, or null if there is no such element.</p>
 
-  <p id="bc-container-document">The <dfn data-x="nav-container-document">container document</dfn>
-  of a <span>navigable</span> <var>navigable</var> is the result of running these steps:</p>
+  <p id="bc-container-document">The <dfn export for="navigable"
+  data-x="nav-container-document">container document</dfn> of a <span>navigable</span>
+  <var>navigable</var> is the result of running these steps:</p>
 
   <ol>
    <li><p>If <var>navigable</var>'s <span data-x="nav-container">container</span> is null, then