Item Update Event is not triggering upon applying filter condition

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we are trying to capture Item Update business event in OIC with a specific condition. i.e capture only Master organization related events and neglect rest of them. To handle this, we have introduced filter condition during event subscription in OIC as below
<xpathExpr xmlns:ns0="http://xmlns.oracle.com/apps/scm/productModel/items/itemServiceV2/types/&quot; xmlns:ns1="http://xmlns.oracle.com/apps/scm/productModel/items/itemServiceV2/">$eventPayload/ns0:result/ns1:OrganizationCode='FE_ITEM_MASTER'</xpathExpr&gt;

We are able to capture events it we don't apply any filter condition whereas if we apply this filter condition it is not working. Any suggestions ?