unplanned depreciation negative in Derived depr area ECC 6.0

We are trying to post unplanned depreciation in Book1 using ttype 641 and the system is not allowing us to post, as we have a derived depreciation area for

Book vs Macrs..

The message is AA639

Unplanned depreciation is negative in area 25.....Where area 25 is the derived depreciation area.

Any suggestions to overcome this as we only want to post to book1.

Thank you