Jupyterhub-idle-culler SSL certificate problem

Running jupyterhub-idle-culler on the same server as Jupyterhub with TLS set up. If I use the full URL with https the following error appears:

tornado.curl_httpclient.CurlError: HTTP 599: SSL certificate problem: unable to get local issuer certificate

If I use `http://localhost’ then it says:

tornado.curl_httpclient.CurlError: HTTP 599: Empty reply from server

Certificate works with everything else, including the browser installed on the server.

Have anyone encountered this problem before? Googling around I found suggestions to overwrite Tornado’s AsyncHTTPClient, which hardly seems like an ideal solution.