I need to be able to wrap this piece of XML in a CDATA section:

        <description>
          <span style="font-size: 11px; color: #000000; font-family: Arial, Helvetica, sans-serif">
            <xsl:value-of select="data[@alias = 'text']" />
          </span>
        </description>

So the result should look like this:

<description><![CDATA[<span style="font-size: 11px; color: #000000; font-family: Arial, Helvetica, sans-serif">Deze nieuwsbrief wordt u gratis aangeboden door xxx (normale abonnementsprijs € 12,95 per jaar).</span>]]></description>

However, when I change the XML output tag to do so, it doesn't wrap anything in CDATA:

<xsl:output method="xml" omit-xml-declaration="yes" cdata-section-elements="description content:encoded"/>

When I do the same thing but I remove the <span> around the <xsl:value-of>, the CDATA wrapper gets produced just fine. 

Of course when I add the span to the rich text editor (the "text" property is of type RTE), it works just fine, but that's not something I want my editors to have to worry about.

So how do I do this?