diff --git a/source b/source
index 6864679188e..dee4ad75a23 100644
--- a/source
+++ b/source
@@ -71832,8 +71832,9 @@ END:VCARD</pre>
 
   <p>The <dfn><code data-x="dom-tabIndex">tabIndex</code></dfn> IDL attribute must
   <span>reflect</span> the value of the <code data-x="attr-tabindex">tabindex</code> content
-  attribute. Its default value is 0 for elements that are focusable and &#x2212;1 for elements that
-  are not focusable.</p>
+  attribute. Its default value is 0, if this element is <span data-x="focusable
+  area">focusable</span> and reachable using <span>sequential focus navigation</span>, and &#x2212;1
+  otherwise.</p>
 
   </div>