diff --git a/source b/source
index 1d93e80b48b..b3111db392e 100644
--- a/source
+++ b/source
@@ -129755,7 +129755,10 @@ iframe { border: 2px inset; }
 
   <pre><code class="css">@namespace "http://www.w3.org/1999/xhtml";
 
-<span id="img-contain-size">img:is([sizes="auto" i], [sizes^="auto," i]) { contain: size !important; }</span></code></pre>
+<span id="img-contain-size">img:is([sizes="auto" i], [sizes^="auto," i]) {
+  contain: size !important;
+  contain-intrinsic-size: 300px 150px;
+}</span></code></pre>
 
   <p>The following CSS rules are expected to apply when the <code>Document</code> is in <span>quirks
   mode</span>:</p>