The gem doesn't recognize the `exiftool` command even when it's installed. That's because Windows' `null device` doesn't follow the POSIX rules. I added the gem 'os' to the file exiftool.rb. require 'os' I changed line #60 to cmd = "#{self.class.command} #{exiftool_opts} -j -coordFormat \"%.8f\" #{escaped_filenames} 2> #{OS.dev_null}" and that did it for me.