Movement type without ref. to a PO

hi,

i am doing a MIGO when i do all the things it show me an error

"You cannot switch to a movement type without ref. to a PO

Message no. MIGO030

Diagnosis

You have replaced the movement type suggested with another movement type that does not refer to a purchase order.

Procedure

Make sure your entries are correct.

Choose a movement type from the list of possible entries."

please suggest what action i have to take

Regards

Maashish