Fails to get tactics from server when using --rating

[SimonKvantdator]

I am getting an error,

$ tactics-trainer --rating=600-1200
thread 'main' panicked at 'Failed to get a new tactic from the server, exiting.: error decoding response body: EOF while parsing a value at line 1 column 0

Caused by:
    EOF while parsing a value at line 1 column 0', /home/simonj/.cargo/registry/src/github.com-1ecc6299db9ec823/tactics-trainer-cli-1.0.2/src/main.rs:65:6
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

whenever I use the --rating option.
Just typing tactics-trainer works fine though.