--- a/encrypted-media/encrypted-media.html	Tue Jan 07 07:51:35 2014 -0800
+++ b/encrypted-media/encrypted-media.html	Tue Jan 07 08:48:53 2014 -0800
@@ -639,7 +639,7 @@
        </li>
     </ol>
 
-    <p>The <dfn id="dom-sourcekeysystem"><code>keySystem</code></dfn> attribute of <code><a href="#dom-htmlsourceelement">HTMLSourceElement</a></code> specifies the <a href="#key-system">Key System</a> to be used with the <code><a href="http://www.w3.org/TR/html5/embedded-content-0.html#media-resource">media resource</a></code>.
+    <p>The <dfn id="dom-sourcekeysystem"><code>keySystem</code></dfn> attribute of <code><a href="#dom-htmlsourceelement">HTMLSourceElement</a></code> specifies the <a href="#key-system">Key System</a> to be used with the <code><a href="http://www.w3.org/TR/html5/embedded-content-0.html#media-resource">media resource</a></code>. The <dfn id="dom-keysystem"><code>keySystem</code></dfn> attribute must be supported by all HTMLSourceElement as both an IDL attribute and also a content attribute named <dfn id="dom-sourcecontentkeysystem"><code>keysystem</code></dfn>.
     The <a href="http://www.w3.org/TR/html5/embedded-content-0.html#concept-media-load-algorithm">resource selection algorithm</a> is modified to check the <code><a href="#dom-sourcekeysystem">keySystem</a></code> attribute after the existing <em>step 5</em> of the <em>Otherwise</em> branch of <em>step 6</em>:
     </p>
     <ol start="6">

--- a/encrypted-media/encrypted-media.xml	Tue Jan 07 07:51:35 2014 -0800
+++ b/encrypted-media/encrypted-media.xml	Tue Jan 07 08:48:53 2014 -0800
@@ -614,7 +614,7 @@
        </li>
     </ol>
 
-    <p>The <codedfn prefix="source">keySystem</codedfn> attribute of <coderef>HTMLSourceElement</coderef> specifies the <a href="#key-system">Key System</a> to be used with the <videoref name="media-resource">media resource</videoref>.
+    <p>The <codedfn prefix="source">keySystem</codedfn> attribute of <coderef>HTMLSourceElement</coderef> specifies the <a href="#key-system">Key System</a> to be used with the <videoref name="media-resource">media resource</videoref>. The <codedfn>keySystem</codedfn> attribute must be supported by all HTMLSourceElement as both an IDL attribute and also a content attribute named <codedfn prefix="sourcecontent">keysystem</codedfn>.
     The <resource-selection-algorithm/> is modified to check the <coderef prefix="source">keySystem</coderef> attribute after the existing <em>step 5</em> of the <em>Otherwise</em> branch of <em>step 6</em>:
     </p>
     <ol start="6">