`bind` not allowed in `where` ???

[VladimirAlexiev]

declare function local:rdf_property ($property, $id as xs:string) {
  let $propName := $property/name()
  let $value    := $property/text()
  for $val where {
    bind(?value as ?val)
  }
  construct {<{$id}> <{$propName}> {$val}}
};

()

fails with

line 4:11 no viable alternative at input 'where'
line 5:4 mismatched input 'bind' expecting RCURLY

But according to https://rawgit2.com/VladimirAlexiev/xsparql/master/doc/grammar.xhtml#sparqlForClause, bind is allowed in where.
Commenting out the bind shows that is the selected grammar branch:

xsparql -a test.xsparql
....
              XSPARQL FOR from 4:6
              T_LET
                $_aux_results1
                T_FUNCTION_CALL
                  _xsparql:_sparqlQuery
                  T_PARAMS
                    T_FUNCTION_CALL
                      fn:concat
                      T_PARAMS
                        $_sparql_prefixes
                         SELECT $val
 where  {  }
                    deleteNode

What is going on?