No selection of primefaces

Hello friends I have a datatable of primefaces with the functionality of selection but it does not work for me, it enters the method rowSelect (), but in event the null object arrived. Attached code that I have implemented, if someone knows what happens, please help me:

            <p:ajax event="rowSelect" listener="#{dialogCuentasContablesController.rowSelect}"/>


        </p:dataTable>      

/// bean public void rowSelect (SelectEvent event) {         PLAnDs with PLAns = (With PLAnsDto) event.getObject ();         setCountable Account (withPlants);     }