Python SDK DropboxTeam.as_user throws BadInputException app_key is required to refresh tokens

dbx_t = dropbox.DropboxTeam(
    oauth2_refresh_token=refresh_token, 
    app_key=app_key, 
    app_secret=app_secret 
) 
admin = dbx_t.team_token_get_authenticated_admin()
dbx_t.as_user(admin.admin_profile.team_member_id)

this raises

File "venv/lib/python3.6/site-packages/dropbox/dropbox.py", line 715, in as_user
    team_member_id)
File "venv/lib/python3.6/site-packages/dropbox/dropbox.py", line 739, in _get_dropbox_client_with_select_header
    headers=new_headers,
File "venv/lib/python3.6/site-packages/dropbox/dropbox.py", line 185, in __init__
    raise BadInputException("app_key is required to refresh tokens")
dropbox.dropbox.BadInputException: app_key is required to refresh tokens

Am I using DropboxTeam.as_user incorrectly?

I looked into the code at dropbox/dropbox.py line 739. It seems like the app_key and app_secret arguments are not passed to the new Dropbox instance.