ERROR (Kamal::ConfigurationError): proxy: Specify one of 'host' or 'hosts', not both

I just changed my config based on this section of documentation from

proxy:
  ssl: false
  forward_headers: true
  host: myapp.dev

to

proxy:
  ssl: false
  forward_headers: true
  hosts:
    - myapp.dev
    - files.myapp.dev

And I'm getting ERROR (Kamal::ConfigurationError): proxy: Specify one of 'host' or 'hosts', not both.

Any idea what might be the problem?

Kamal version 2.11.0