Update table from different table

UPDATE RBI.RBI_OV_F_DETAIL A
     SET (BRANCH_ID, BRANCH_NUMBER) = (
           SELECT PRICE_BRANCH_ID, PRICE_BRANCH
             FROM RSE.RSE_SO_F_ORDERS B
                WHERE A.SOURCE_ID = B.FULL_ORDER_NUMBER AND A.METRIC_GROUP_ID='1');

I am getting error in this syntax:
single query returns multiple rows

Please suggest what to do.