Msg. RE012 during GI with reference to Reservation

Dear gurus,

I need to have budget availability check in the time when I create reservation from the stock. Because of that I activated Business Function PSM_FM_CI_1. Now when I create material reservation everything is ok. But when I try to post GI with reference on previously created reservation I get message RE012 - Reduction not possible; doc &1 has a doc cat. (&2) that is not allowed. Do you have any advice how to solve this problem?

Thank you in advance,

Harry