Error despite enabling tif output

I've setup loris with tif enabled in the target_formats list, however I get a server error when trying to get that output format on one of the example images:

2019-11-14 17:22:31,288 (werkzeug) [INFO]: 192.168.48.3 - - [14/Nov/2019 17:22:31] "GET /01/02/0001.jp2/1000,1000,1500,1200/full/0/default.tif HTTP/1.0" 500 -
2019-11-14 17:22:31,291 (werkzeug) [ERROR]: Error on request:
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/werkzeug/serving.py", line 193, in run_wsgi
    execute(self.server.app)
  File "/usr/local/lib/python2.7/dist-packages/werkzeug/serving.py", line 181, in execute
    application_iter = app(environ, start_response)
  File "/opt/loris/loris/webapp.py", line 360, in __call__
    return self.wsgi_app(environ, start_response)
  File "/opt/loris/loris/webapp.py", line 254, in wsgi_app
    response = self.route(request)
  File "/opt/loris/loris/webapp.py", line 290, in route
    return self.get_img(request, ident, region, size, rotation, quality, fmt, base_uri)
  File "/opt/loris/loris/webapp.py", line 567, in get_img
    r.last_modified = datetime.utcfromtimestamp(path.getctime(fp))
  File "/usr/lib/python2.7/genericpath.py", line 64, in getctime
    return os.stat(filename).st_ctime
OSError: [Errno 2] No such file or directory: '/var/cache/loris2/01/02/0001.jp2/1000,1000,1500,1200/full/0/default.tif'

JPG and PNG requests work just fine. I'm guessing the conversion is choking somewhere? I've reinstalled Pillow and it confirms that it's got access to libtiff...

loris-imageserver / loris

Error despite enabling tif output #489