child zone checking is broken

Steps to reproduce:

Create a domain example.com
Create a domain db.example.com

create a record somedb.example.com in the example.com domain

Error:

+---------+--------------------------------------------------------------+
| Field | Value |
+---------+--------------------------------------------------------------+
| Code | 400 |
| Type | invalid_recordset_location |
| Message | RecordSet belongs in a child zone: db.example.com. |
+---------+--------------------------------------------------------------+