Setup for Expense charge account in PO

Hi!!

Is there any additional setup to automatically default the expense charge account in a Purchase Order beside the following actions:

1. I have put a Default Expense Account in the Employee Assignment of the requester

2. I have configured Expense Charge Account Rules

3. I'm filling the Requester at the PO.

For some reason the PO charge account is not getting defaulted. Im buying categories not items.

Thanks in advance!