Custom domain does not work with SSH

[tcz]

I'm trying to set up SSH access to a Raspberry Pi behind firewall. I need it to have a custom domain. I have Ngrok PRO.

I added a custom domain on the web, yet when I try to set up Ngrok with the following command:

/usr/local/bin/ngrok tcp 22 --domain olivera.ngrok.dev

...I get the following error:

ERROR:  unknown flag: --domain

With HTTP it works perfectly fine:

/usr/local/bin/ngrok http 80 --domain olivera.ngrok.dev


$ ngrok -v
ngrok version 3.9.0