F-02 Field Status Group

Dear SAP guru,

I encountered an issue regarding field status group.

My client requirement is to make WBS field mandatory for G/L account 1221XXX (customer DEPOSIT ACCOUNT ).

I have created customized field status variant Z100 in which WBS field is set to required, I assigned FSV Z100 to G/L account 1221xx(customer deposit a/c) and 2221xx (customer down payment a/c).

In T-code F-02 I made entries as follow:

Dr. Posting Key 40 A/C 1001 CASH $100

Cr Posting Key 19 A/C 1221XXX $100 (here I gave Special G/L indicator 'E' for customer deposit)

The system allows me to post above entries without having to specify WBS NO..

The strange thing is this is working fine for G/L account 2221xx (customer down payment ) which the system prompts user to key in WBS No.

I have check posting key 19 in which all data fields are set to optional.

What could be the cause for this and am I missing something?

Appreciated for any valuable inputs

BAI JL