ERR_CONTENT_LENGTH_MISMATCH when using ember-prerender

I've inherited an Ember.js project that uses ember-prerender for SEO. I have the following ember-prerender config:

var prerender = require('ember-prerender/lib');

var config = {
  "port": parseInt(process.env.PORT) || 4000,
  "processNum": 0,
  "engine": "phantom",
  "contentReadyDelay": 0,
  "initializeTimeout": 25000,
  "renderTimeout": 15000,
  "maxRequestsPerRenderer": 100,
  "maxQueueSize": 1000,
  "appUrl": "http://localhost:3000/",
  "initializeUrl": "",
  "applicationPage": "index.html",
  "serveFiles": true,
  "filesMatch": "/\\.(?:css|js|jpg|png|gif|ico|svg|woff|ttf|swf|map)(?:\\?|$)/i",
  "logging": {
    "level": "debug",
    "timestamp": true,
    "format": true
  },
  "plugins": [
    "removeScriptTags",
    "httpHeaders"
  ]
};

var server = prerender(config);
server.start();

The app is able to start up successfully. However, when I browse to http://localhost:4000/, it gives the following error in the browser console:

GET http://localhost:4000/ net::ERR_CONTENT_LENGTH_MISMATCH

Here's the header info from the initial request:

Request URL:http://localhost:4000/
Request Method:GET
Status Code:200 OK
Remote Address:127.0.0.1:4000


# Response Headers

Connection:keep-alive
Content-Length:800111
Content-Type:text/html;charset=UTF-8
Date:Tue, 19 Jan 2016 14:26:49 GMT


# Request Headers

Accept:text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Accept-Encoding:gzip, deflate, sdch
Accept-Language:en-US,en;q=0.8,es;q=0.6
Cache-Control:no-cache
Connection:keep-alive
Host:localhost:4000
Pragma:no-cache
Upgrade-Insecure-Requests:1
User-Agent:Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_2) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/47.0.2526.111 Safari/537.36

Any ideas of what's happening?