Error in MIGO (problem with condition not allowing any wbs element)

Hi gurus,

i have created project using with project type, then i want to restrict business transactions for wbs elements.

Validation :  Prerequisite is   PRPS-PRART = 'SM'

                      Check is             "COBL-SAKNR IN SET_SM OR COBL-SAKNR IN SET_SM"

                      Message is          Assign Proper wbs element.

Here SM is Project type and SET_SM contains related project type of GL's.

When i am creating PR or PO the condition is working fine(i.e.it is not allowing any other wbs elements)

Now the problem is when i am trying to create MIGO using same PO the above condition is not working, i.e the WBS element which is used in the PO is not accepting while creating MIGO.

Example: 1.SM is Project type and SET_SM is Set. my wbs element is AS-00000039-01. Account assignment category is 'Q'.

                2 I have maintained 3 procurement GL's those are 203010,203020, 203040 in SET_SM

                3.using transaction code ME21N i am creating PO successfully against above specified WBS element

                4.when i am trying to creating MIGO against same PO i am getting error message like "Assign Proper wbs element".

Kindly provide the solution how to rectify this problem also find the attached procedure document.