Loading Hidden sheet

[rafspiny]

In the Excel2007 reader I'm having problems loading hidden sheets.
The reader won't load those sheet.

Snippet of code

$objPHPExcel = PHPExcel_IOFactory::load($inputFileName);
$objPHPExcel->getAllSheets();
$objPHPExcel->getSheetByName('hidden_sheet');
$objPHPExcel->getSheetByCodeName('hidden_sheet');

Neither using the iterator gives me the hidden sheet

foreach ($objPHPExcel->getWorksheetIterator() as $worksheet) {
        $title = strtolower(trim($worksheet->getTitle()));
        echo $title;
}

Am I missing something?
I opened the xlsx file, the hidden sheets seems to not be present in the list in the xl/workbook.xml file.