text filter not including value with request to server with Ajax POST

Question

I am using YADFC to add filtering to a DT table, with good success on select filter elements. But text filter elements do not send any value to the server (although they do fire a request to the server). What could I be missing?

            yadcf.init(myTable, [
            {
                column_number : 0,
                filter_type   : 'select'
            },
            {
                column_number : 1,
                filter_type   : 'select'
            },
            {
                column_number : 2,
                filter_type   : 'select'
            },
            {
                column_number : 3,
                filter_type   : 'text',
                filter_delay  : 500
            },

But the param comes to the server with no value, when I type in the field:

  'columns[3][data]'          => 'username',
  'columns[3][name]'          => '',
  'columns[3][orderable]'     => 'true',
  'columns[3][search][regex]' => 'true',
  'columns[3][search][value]' => '',
  'columns[3][searchable]'    => 'true',

FWIW I get the same behaviour with auto_complete filter.

Thanks for any help!