I am attempting to update mongo ssl configuration which is deprecated in 4.2 to tls configuration.

$ cat /etc/mongod.conf | grep -A 6 net:
net:
port: 27017
bindIp: 127.0.0.1,10.131.27.67
tls:
mode: requireSSL
certificateKeyFile: [CERTS_DIR]/server/mongo-server.pem
CAFile: [CERTS_DIR]/ca/mongo-ca.crt

Yet when I start mongo it prints this error:

Oct 15 07:23:22 datastore02 mongod[20128]: 2019-10-15T07:23:22.593+0100 F CONTROL [main] Failed global initialization: BadValue: unsupported value for tlsMode requireSSL

Docs say this value is supported.