diff --git a/fetch.bs b/fetch.bs
index 625f5bd71..872257d65 100644
--- a/fetch.bs
+++ b/fetch.bs
@@ -5654,6 +5654,12 @@ run these steps:
     default), and `<code>Accept-Charset</code>` is a waste of bytes. See
     <a>HTTP header layer division</a> for more details.
 
+   <li><p>If <var>httpRequest</var>'s <a for=request>header list</a>
+    <a for="header list">does not contain</a> `<code>Priority</code>`, then user agents may
+    <a for="header list">append</a> a `<code>Priority</code>` <a>header</a> with an
+    <a>implementation-defined</a> value derived from <var>httpRequest</var>'s
+    <a for=request>internal priority</a> in accordance with RFC 9218. [[!RFC9218]]
+
    <li>
     <p>If <var>includeCredentials</var> is true, then: