--- a/webaudio/specification.html	Wed May 22 13:16:46 2013 -0700
+++ b/webaudio/specification.html	Wed May 22 17:06:18 2013 -0400
@@ -1413,7 +1413,9 @@
   <dt id="dfn-channelCount"><code>channelCount</code><dt>
     <dd><p>The number of channels used when up-mixing and down-mixing connections to any inputs to the node.  The default value is 2
        except for specific nodes where its value is specially determined.
-       This attribute has no effect for nodes with no inputs.</p>
+       This attribute has no effect for nodes with no inputs.
+       If this value is set to zero, the implementation MUST raise the
+       NOT_SUPPORTED_ERR exception.</p>
       <p>See the <a href="#UpMix-section">Channel up-mixing and down-mixing</a>
         section for more information on this attribute.</p>
     </dd>