diff --git a/source b/source
index be68617c889..c383e48bbba 100644
--- a/source
+++ b/source
@@ -27725,6 +27725,9 @@ was an English &lt;a href="/wiki/Music_hall">music hall&lt;/a> singer, ...</code
     </ol>
    </li>
 
+   <li><p>If another instance of this algorithm for this <code>img</code> element was started after
+   this instance (even if it aborted and is no longer running), then return.</p></li>
+
    <li>
     <!--FETCH-->
     <p><span data-x="concept-fetch">Fetch</span> <var>request</var>. Let this instance of the <span