Socket hang up error

Since upgrading to Ember 1.13.2 and Ember Data 1.13.4. I've been receiving the following error once in a while. This only happens when I manually refresh the page.

What could be causing this?

Error proxying to http://localhost:3099/
socket hang up
Error: socket hang up
    at createHangUpError (_http_client.js:215:15)
    at Socket.socketCloseListener (_http_client.js:247:23)
    at Socket.emit (events.js:129:20)
    at TCP.close (net.js:485:12)