UTF in uploaded filename

If you upload a file with a special character to http://www.smartclient.com/smartgwte...se/#upload_sql , you cannot download it correctly.

E.g.:
filename: ać.txt
Upload, View as List
Display name: ać.txt (correct!)
Click in download arrow:
filename: a_.txt (incorrect) (In firefox 26)
filename: a-.txt (incorrect) (In chrome 37)

Is it possible to correct this?
I read on the internet (http://greenbytes.de/tech/tc2231/) this should be set:
Header Content-Disposition=attachment; filename*=UTF-8''" + encodedFilename + ".xls"
with encodedFilename = URLEncoder.encode(
filenameAsString, "UTF-8");
But as this is an automatic smartgwt feature, I think I cannot set this header.