CasperJS and SlimerJS couldn't get pref: extensions.getAddons.cache.enabled

Question

I am trying to test a navigation menu by making CasperJS to click on different parts of the menu. After the first couple of clicks Slimerjs is hanging and after 5 minutes or so I'm getting the following error: addons.repository WARN cacheEnabled: Couldn't get pref: extensions.getAddons.cache.enabled".

This is how I run my test:

casperjs test tests/ --engine=slimerjs --verbose

And here's my code:

casper.test.begin('Deal menu is working as expected', 2, function suite(test) {
  casper.start('http://username:password@somesite/section/home', function() {
    test.assertTitle('Main Page', 'Main Page loaded');
    casper.capture('mainPage.png');
  });

  casper.then(function() {
    this.click('#menuId1');
    this.wait(2000, function() {
      test.assertTitle('Menu 1', 'Menu 1 loaded');
      casper.capture('pic1.png');
    });
  });

  casper.then(function() {
    this.click('#menuId2');
    this.wait(2000, function() {
      test.assertTitle('Menu 2', 'Menu 2 loaded');
      casper.capture('pic2.png');
    });
  });

  casper.then(function() {
    this.click('#menuId3');
    this.wait(2000, function() {
      test.assertTitle('Menu 3', 'Menu 3 loaded');
      casper.capture('pic3.png');
    });
  });

  casper.run(function() {
    test.done();
  });
});

After the second casper.then it hangs and after a while it gives me the error message I mentioned above. I've also checked firefox (version 39) that extensions.getAddons.cache.enabled is equal to true.

When I run the same test with PhantomJS it works fine. Any ideas?