Cannot redirect to FTP link

Steps to reproduce:
1. go to http://metamark.net/
2. enter URL from FTP sites, example ftp://ftp.osuosl.org/pub/software/graphics/pngtoico/
3. click "shorten" button
4. URL shortened successfully as http://xrl.us/oo2wp
5. go to http://xrl.us/oo2wp

Expected result:
redirected to ftp://ftp.osuosl.org/pub/software/graphics/pngtoico/

Actual result:
opened http://xrl.usftp//ftp.osuosl.org/pub/...