diff --git a/complete.html b/complete.html
index 23c571b6e3e..d6e7df86ec9 100644
--- a/complete.html
+++ b/complete.html
@@ -26874,6 +26874,15 @@ <h4 id=the-iframe-element><span class=secno>4.8.2 </span>The <dfn><code>iframe</
    browsing context</a> unless an <a href=#explicit-self-navigation-override>explicit self-navigation
    override</a> is used (<code title="">target="_self"</code>).</li>
 
+   <li><p>Media queries in the context of the <code><a href=#the-iframe-element>iframe</a></code>'s
+   <a href=#browsing-context>browsing context</a> (e.g. on <code title=attr-style-media><a href=#attr-style-media>media</a></code> attributes of
+   <code><a href=#the-style-element>style</a></code> elements in <code><a href=#document>Document</a></code>s in that
+   <code><a href=#the-iframe-element>iframe</a></code>) must be evaluated with respect to the nearest
+   <a href=#ancestor-browsing-context>ancestor browsing context</a> that is not itself being
+   <a href=#browsing-context-nested-through title="browsing context nested through">nested through</a>
+   an <code><a href=#the-iframe-element>iframe</a></code> that is <a href=#in-seamless-mode>in seamless
+   mode</a>. <a href=#refsMQ>[MQ]</a></li>
+
    <li><p>In a CSS-supporting user agent: the user agent must add all
    the style sheets that apply to the <code><a href=#the-iframe-element>iframe</a></code> element to
    the cascade of the <a href=#active-document>active document</a> of the
diff --git a/index b/index
index 23c571b6e3e..d6e7df86ec9 100644
--- a/index
+++ b/index
@@ -26874,6 +26874,15 @@ href="?audio"&gt;audio&lt;/a&gt; test instead.)&lt;/p&gt;</pre>
    browsing context</a> unless an <a href=#explicit-self-navigation-override>explicit self-navigation
    override</a> is used (<code title="">target="_self"</code>).</li>
 
+   <li><p>Media queries in the context of the <code><a href=#the-iframe-element>iframe</a></code>'s
+   <a href=#browsing-context>browsing context</a> (e.g. on <code title=attr-style-media><a href=#attr-style-media>media</a></code> attributes of
+   <code><a href=#the-style-element>style</a></code> elements in <code><a href=#document>Document</a></code>s in that
+   <code><a href=#the-iframe-element>iframe</a></code>) must be evaluated with respect to the nearest
+   <a href=#ancestor-browsing-context>ancestor browsing context</a> that is not itself being
+   <a href=#browsing-context-nested-through title="browsing context nested through">nested through</a>
+   an <code><a href=#the-iframe-element>iframe</a></code> that is <a href=#in-seamless-mode>in seamless
+   mode</a>. <a href=#refsMQ>[MQ]</a></li>
+
    <li><p>In a CSS-supporting user agent: the user agent must add all
    the style sheets that apply to the <code><a href=#the-iframe-element>iframe</a></code> element to
    the cascade of the <a href=#active-document>active document</a> of the
diff --git a/source b/source
index b60301bd6b1..9388cd13f45 100644
--- a/source
+++ b/source
@@ -28977,6 +28977,16 @@ href="?audio">audio&lt;/a> test instead.)&lt;/p></pre>
    override</span> is used (<code
    title="">target="_self"</code>).</p></li>
 
+   <li><p>Media queries in the context of the <code>iframe</code>'s
+   <span>browsing context</span> (e.g. on <code
+   title="attr-style-media">media</code> attributes of
+   <code>style</code> elements in <code>Document</code>s in that
+   <code>iframe</code>) must be evaluated with respect to the nearest
+   <span>ancestor browsing context</span> that is not itself being
+   <span title="browsing context nested through">nested through</span>
+   an <code>iframe</code> that is <span>in seamless
+   mode</span>. <a href="#refsMQ">[MQ]</a></p></li>
+
    <li><p>In a CSS-supporting user agent: the user agent must add all
    the style sheets that apply to the <code>iframe</code> element to
    the cascade of the <span>active document</span> of the