Downloaded translated .pot file has no extension

If the user uploads a .pot file to File project, translates it, then downloads it, Zanata serves a file with no extension and displays ".null" in the menu option.
See screenshot.

1. Create/access a File project and version
2. Upload a .pot file for translation
3. Select a language in the languages tab, then click the V (down) arrow on the file

• Note the option indicates "Download translated "
  4. Select the Download option

Actual:
File downloaded without extension

Expected:
File with .pot extension downloaded