Change the Unit of measure in Material master

Hi friends,

i need to change the basic unit of measure in Material master.

the procedure which i have done is explained below

stock related to special stock is lying in Inventory.

there are no Open PO's as of now.

i have done 562-Q in order to make teh inventory to Zero.

i have changed the Basic unit of measure in Material Master

when i am reversing the material document it is showing

"stock keeping unit in the material master differs with stock keeping unit in material document".

Kindly tell me the exact Procedure of doing this

Points will be rewarded for the solution