Obscure python syntax error

Been writing python for a long time. When I wrote this code, I could not figure out why I was getting a syntax error.


d1 = dict(
    user_id=99,
    display_name='Matt Wilson',)

d2 = dict(
    email_address='matt@tplus1.com',
    **d1,)

It is the trailing comma after **d1. It is not OK. Which is really weird, because the trailing comma after display_name=’Matt Wilson’ is just fine.