Concat function not working in MySQL stored procedure

Question

I have a statement in the stored procedure:

SELECT 
    IFNULL(UnitValue,0) INTO v_Pump_DayEnd_Value,
    CONCAT(Dated,' ', Timed, ' - ', IFNULL(UnitValue, 0)) 
INTO 
    v_PumpEndValueAndTime, CustomName
FROM 
    DeviceSensorData
WHERE 
    (CustomName = 'PUMP' OR CustomName = 'PUMP A' OR CustomName = 'PUMP B') 
    AND SensorName LIKE '%Total%'
    AND Device = v_DeviceID
    AND Dated = DATE(NOW())
ORDER BY 
    ID DESC
LIMIT 1;

The error I get is

Error Code: 1327
Undeclared variable: CONCAT