pssh on mac 10.14 "Command not specified"

Question

I have installed pssh 2.3.1 on my mac mojave 10.14

brew install pssh
pssh --version
2.3.1

pssh --help also works fine. But when I try this:

pssh -H "10.65.8.50 10.65.8.45" -l dev
Usage: pssh [OPTIONS] command [...]

pssh: error: Command not specified.

I have python 3.7.5 installed. What am I doing wrong here?? :)