sinonjs Karma tests in IE Fail to run

So we have been running unit tests with our configuration with no issues using Chrome, however we finally got a build server made and want to run automated tests across all the browsers we support during the CI process. I had no problem integrating karma into the TFS build and getting it to run, however upon trying to add IE into the mix things just blew up. Upon inspecting the issue in the debugger during a watch session I see that sinonjs is bundling an arrow function into my code which of course IE will not like and stop the tests from running. I am confused here as the sinonjs site says it supports IE11. What do I need to do to use sinon in IE?

Karma.conf.js

var webpackConfig = require('./webpack.config.js')

module.exports = function (config) {
    config.set({
      browsers: ['IE'],
      files:[
           'Areas/Dashboard/test/**/*.spec.js'
      ],
      plugins:[ 'karma-ie-launcher',
        'karma-chai',
        'karma-coverage',
        'karma-mocha',
        'karma-webpack'],
      preprocessors: {
        'Areas/Dashboard/test/**/*.spec.js': ['webpack','sourcemap']
      },
      webpack: webpackConfig,
      singleRun: false

    });
}