ARQ converting boolean to integer?

[Bob DuCharme]

http://www.w3.org/TR/2010/WD-sparql11-query-20101014/#FunctionMapping 
gives me the impression that conversion of a boolean to an integer 
should work, but this query

   PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
   SELECT ?oInt WHERE {
      ?s ?p ?o .
      BIND (xsd:integer(?o) as ?oInt )
   }
just comes up blank with this data:

   @prefix xsd: <http://www.w3.org/2001/XMLSchema#> .
   @prefix ex: <http://ex/> .

   ex:thing1 ex:required "true"^^xsd:boolean .

I'm using ARQ 2.8.8. Shouldn't it turn true into a 1 and false into a 0? 
(Then again, the part of the spec referenced above says that this is 
"allowed," not "required"...)

thanks,

Bob