IE11 converting .xlsx files to .xls and .docx files to .doc

I have a java application where users can upload and download files. Recently, we found out that whenever users click on a link on IE11 to download .docx or a .xlsx file, it downloads a .doc or .xls file. In the process, it warns the users that the file format and extension do not match and the users should only open the file if they trust its source. There is no such issue on Microsoft Edge or other browsers.
Is there some setting that can be done in IE11 or can some coding (specific to IE11) be done so that so that it downloads .xlsx and .docx files as they are and doesn't give annoying warning messages to users?

			try {
byte[] fileContent = getFileContent(id, fName);
if (fileContent != null) {
OutputStream out = null;
try {
System.out.println("content type: "+getContentType(fName)); //prints application/vnd.ms-excel
res.reset();
out = res.getOutputStream();
res.setContentType(getContentType(fName));
res.setHeader("Content-Disposition", "inline; filename=" + fName + "; size=" + String.valueOf(fileContent.length));
res.setContentLength(fileContent.length);
out.write(fileContent);
setDestination(req, RESPONSE_NO_REDIRECT);
} catch (Exception ex) {
ex.printStackTrace();
} finally {
flushCloseOutputStream(out);
}
} else {
setDestination(req, "/404.jsp");
}
} catch (Exception ex) {
ex.printStackTrace();
}
public byte[] getFileContent(int id, String fileName) {
byte[] bytes = null;
Transaction tx = null;
Session s = null;
try {
GenericDAO dao = HibernateDAOFactory.getInstance().getDAO(GenericClassDAO.class, Files.class);
s = SessionAndTransactionManagementService.createNewSession(dao);
tx = SessionAndTransactionManagementService.startNewTransaction(s);
Criteria cr = s.createCriteria(Files.class)
.add(Restrictions.eq("id", id))
.add(Restrictions.eq("fileName", fileName))
.setProjection(Projections.property("fileContent"));
bytes = (byte[]) cr.uniqueResult();
SessionAndTransactionManagementService.commitTransaction(s);
} catch (Exception e) {
HibernateUtil.rollback(tx);
}finally{
HibernateUtil.cleanupResources(s);
}
return bytes;
}

IE11 was setting content type for all excel files as 'application/vnd.ms-excel' (don't know why). That makes it show warnings and download xlsx files as xls.

I changed my code to set contentType manually to 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet' when the filename contains .xlsx and this solved my problem.