is it possible to obtain the query plan via the BaseX REST interface?

I tried:

curl -i -X POST -H "Content-Type: application/xml" -d "<query xmlns='http://basex.org/rest'><text>some_query_here</text><option name='xmlplan' value='true'/></query>" "http://xyz"

but this only returns the query results, not the plan.

Thanks,

Christian