accept ssl cert with marionette firefox webdrive python splinter

when using python splinter firefox 47 marionette new webdriver, it gives certificate error when access the website i want, i tried to accept ssl certs with

browser = Browser('firefox', capabilities = {'marionette': True, 'acceptSslCerts': True})

or using trustAllSSLCertificates instead of acceptSslCerts, but still gives me certificate error, what is the problem?