I don't know if Bearer is case sensitive, but I am mentioning this because I've seen this be mentioned as a gotcha in other APIs before.

Also, The OAuth 2.0 Authorization Framework: Bearer Token Usage (rfc6750) does mention this:

>Unless otherwise noted, all the protocol parameter names and values are case sensitive.

It doesn't really clear up my confusion, but so generally I make sure to send it with a capital B.