jsxc: Unable to launch application after installation

Launching the application JSXC fails with the following error.

   ERROR django.request       Internal Server Error: /plinth/apps/jsxc/jsxc/
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/django/core/handlers/exception.py", line 34, in inner
    response = get_response(request)
  File "/usr/lib/python3/dist-packages/django/core/handlers/base.py", line 115, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "/usr/lib/python3/dist-packages/django/core/handlers/base.py", line 113, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/usr/lib/python3/dist-packages/django/views/generic/base.py", line 71, in view
    return self.dispatch(request, *args, **kwargs)
  File "/usr/lib/python3/dist-packages/django/utils/decorators.py", line 44, in _wrapper
    bound_method = dec(bound_method)
  File "/usr/lib/python3/dist-packages/stronghold/decorators.py", line 13, in public
    set_view_func_public(orig_func)
  File "/usr/lib/python3/dist-packages/stronghold/utils.py", line 13, in set_view_func_public
    setattr(func, 'STRONGHOLD_IS_PUBLIC', True)
AttributeError: 'method' object has no attribute 'STRONGHOLD_IS_PUBLIC'

FreedomBox on Debian unstable. virtualbox-amd64