BAPI_GOODSMVT_CREATE + autoserial number

Hi,

I have used BAPI_GOODSMVT_CREATE to post initial stock. This function module has table GOODSMVT_ITEM and its field SERIALNO_AUTO_NUMBERASSIGNMENT. I set this field as 'X' so that when I post stocks, serial number is determined automatically.

Unfortunately it posted stock with no serial number. any clue guys why it happened and how this could be corrected.