No direct postings can be made to G/L acct. 50000020 in CoCode 3000 When creating A PO

Hello Gurus,

There is a issue when creating a PO ”No direct postings can be made to G/L acct. 50000020 in CoCode 3000”. I am going to create a Material PO and in account assignment tab the G/L is get as Consumption -Spares A/c. 

A Screenshot is attached FYR. 

Any sustainable solution can provide to create the PO without this issue.