persistent.multi-valued tag

I have a persistent defined:
 * @persist.field
 *   name="my_code_id"
 *   db-name="my_code_id"
 *   type="INTEGER"
 *   length="8"
 *   null-allowed="false"
 *   multi-valued="true"
 *   descrip="The code id"
 * @persist.lookup 
 *   name="occa.my_code" 
 *   field="ID" 
 *   display="code"

but the generated xconf file looks like this (notice the missing
multi-valued tag)

<field
            name="my_code_id"
            type="INTEGER"
            db-name="my_code_id"
            descrip="The code id"
            null-allowed="false"
            length="8"
          >
<lookup     name="occa.my_code"
              field="ID"
              display="code"
            />
</field>

I get these even after an ant clean.  Any ideas why it is dropping the
multi-valued tag?
I'm trying to use getValidValues with my persistent, and it complains
about not being multivalued.

TIA
gene