I can't remove cover image from mobi file

I am trying to remove the cover image from one mobi file but i can't do this with calibre. I am removing the cover image from the "edit metadata" option but it doesn't actually remove it. When i open the file with kindle or Calibre e-book viewer the image is still there.

Is there any way to delete the cover image? I want to completely remove it from the mobi file?