Bridge CS6 metadata palette not creating bag array

I am having trouble getting a custom XML Bridge metadata palette to write bag arrays.

What I want is:

<dcterms:subject>

    <rdf:Bag>

       <rdf:li>term 1</rdf:li>

       <rdf:li>term 2</rdf:li>

       <rdf:li>term 3</rdf:li>

    </rdf:Bag>

</dcterms:subject>

The result I get is:

<dcterms:subject>term 1; term 2; term 3</dcterms:subject>

My code is:

<?xml version="1.0" encoding="UTF-8"?>

<xmp_definitions xmlns:ui="http://ns.adobe.com/xmp/fileinfo/ui/">

<xmp_schema prefix="dcterms" namespace="http://purl.org/dc/terms/" label="$$$/Custom/Schema/dcterms/Label=Dublin Core Terms"/>

<xmp_property prefix="dcterms" name="subject" label="$$$/Custom/Property/dcterms/Subject=Subject" category="external" type="bag" element_type="text"/>   

</xmp_schema>

</xmp_definitions>

This code works in CS4 and CS5.  I don't see any new requirements for XML panels in the CS6 XMP SDK, am I missing something? I also tried writing a simple dc:subject property, but it also failed to create a bag.  The CS6 Bridge IPTC Core palette works correctly, so I have to think this is a problem only for custom palettes.

Thanks,

Greg Reser