I'm generating XLSX spreadsheet using OOXML SDK, and I need to get rid of x: namespace prefix. How can I achieve this?

using (SpreadsheetDocument doc = SpreadsheetDocument.Open("template.xlsx", true))
            {
                //Save the shared string table part
                if (doc.WorkbookPart.GetPartsOfType().Count() > 0)
                {
                    SharedStringTablePart shareStringPart = 
                                       doc.WorkbookPart.GetPartsOfType().First();
                    shareStringPart.SharedStringTable.Save();
                }

                //Save the workbook
                doc.WorkbookPart.Workbook.Save();
}

Here, the original XLSX file is coming from Excel 2007 and doesn't have the prefix, however, after the save operation the prefix appears. How can I avoid that?