Ember FastBoot Cannot read property 'userAgent' of undefined

I'm trying to use Ember FastBoot for my application but when I run: ember fastboot --serve-assets this error is thrown:

Cannot read property 'userAgent' of undefined TypeError: Cannot read property 'userAgent' of undefined at Object.125.global/document (<anonymous>:121923:53) at s (<anonymous>:104896:621) at <anonymous>:104896:672 at Object.106../big-play-button.js (<anonymous>:113849:23) at s (<anonymous>:104896:621) at <anonymous>:104896:672 at Object.139.../../src/js/utils/merge-options.js (<anonymous>:123824:15) at s (<anonymous>:104896:621) at e (<anonymous>:104896:792) at <anonymous>:104896:810

any help?