Amazon Web Services (AWS) - multiple MFAs with root?

Has anybody gotten this to work? If I set up multiple MFA devices with my IAM accounts, they all work flawlessly. But if I set up multiple MFA devices with my root account, only the original MFA device works. No matter how carefully I set up and synch a secondary device, it simply will not work with root. As the linked article says, this should be possible with either root or IAM (though in the past this was not the case). Thanks.