Filtering by file type does not work

Steps to reproduce:

• Attach an mp3 file or text file on a page.
• go to Search Page, and at the "Type" option, select Attachment
• leave the option for "File Type" to All
• Search using a part of your file name. You will see it in the results.
• filter for "File Type" and select Audio or Text file. Search again. You will get no results.
  It seems that ATM, there is no option to filter by file types.