karma junit report crashing

I am trying to run karma on a project, and its crashing on running the junit report, although it works with the same project in a similarly configured machinne.

When trying to run

karma start '<path-to>/karma.conf.js' --reporters junit --single-run --junitReporter.outputFile karmaoutpu

And I am getting this traceback:

INFO [karma]: Karma v0.12.17 server started at http://localhost:9876/
INFO [launcher]: Starting browser PhantomJS
INFO [PhantomJS 1.9.2 (Linux)]: Connected on socket fAqoa8mrX6WgaHTam1Ut with id 5898608
ERROR [karma]: [TypeError: Cannot call method 'push' of undefined]
TypeError: Cannot call method 'push' of undefined
  at [object Object].onBrowserStart (<project-path>/node_modules/karma/lib/reporters/base.js:14:20)

Checking that base.jsfile, I have this snippet:

  this.onRunStart = function() {
    this._browsers = [];
  };

  this.onBrowserStart = function(browser) {
    this._browsers.push(browser);  // <this._browsers is undefined here!>
  };

If I force the initiation of the this._browsers array inside onBrowserStart, I get other errors elsewhere - but this tells me that onRunStart is not being called - so I am probably missing some initialization. What could be that it fails, being that the same project, with the same versions of Node packages work in an Ubuntu system (I am on Fedora 20)

The dots reporter plug-in, on the other hand, works flawlessly.

Versions for karma, and karma related packages installed:

    karma 0.12.17
├─┬ karma-chai@0.0.1
│ └── chai@1.6.1
├── karma-chrome-launcher@0.1.4
├─┬ karma-coffee-preprocessor@0.1.3
│ └─┬ coffee-script@1.7.1
│   └── mkdirp@0.3.5
├── karma-firefox-launcher@0.1.3
├── karma-html2js-preprocessor@0.1.0
├── karma-jasmine@0.1.5
├─┬ karma-junit-reporter@0.1.0
│ └── xmlbuilder@0.4.2
├── karma-mocha@0.1.6
├── karma-phantomjs-launcher@0.1.4
├── karma-requirejs@0.2.2
├── karma-script-launcher@0.1.0
...
├─┬ phantomjs@1.9.2-2