Changing Base UOM for material in APO

Experts,

We have changed the Base UOM for material in ECC. But when transferred the same to APO through CIF we got the error message saying "Base UOM for material can not be changed". I tried changing the UOM manually in APO and got the same message.

Does it mean we can not change the Base UOM once set? Or is there any alternative way to change the UOM.

Please suggest.

Thanks

Pavan Sarda