Order of items on registration page has changed after upgrade to 4.7.6

Hallo,
after upgrading from 4.7.3 to 4.7.6 the order of items an page user/register has changed in a unpleasant manner:
order before:
1. area with account information (usernam and email address)
2. area with my self defined profile fields
order after:
1. area with my self defined profile fields
2. area with account information (usernam and email address)

What went wrong and where can I influence this order?
Thanks in advance for any hints!