nollup: WebSocket connection failed

So close to finally having nollup up and running with HMR! This is my first project where I’ve attempted to use HMR by the way, so I’m sure there are simple things I’m overlooking.

I’m calling nollup like this: nollup -c --hot

The bundle builds without errors and my app loads. But HMR isn’t working and this is in the console:

WebSocket connection to 'ws://__hmr/' failed: Error during WebSocket handshake: Unexpected response code: 200

and the line that’s throwing this error: var ws = new WebSocket('ws://' + window.location.host + '/__hmr');

Any suggestions? Should I be filling something in for --hmr-host?

Thank you!