Using CASE to create new column based on specific data in a column

SELECT field1,
       field2,
       field3,
       fieldname = CASE [field4] 
        WHEN '9' THEN 'Semi Trailer'
        WHEN '7' THEN 'Pole Trailer'
        WHEN '6' THEN 'Other'
        WHEN '5' THEN 'Motor Carrier'
        WHEN '3' THEN 'Full Trailer'
        WHEN '2' THEN 'Dolly Converter'
        WHEN '14' THEN 'Intermodal Chassis'
        WHEN '12' THEN 'Van'
        WHEN '11' THEN 'Truck Tractor'
        WHEN '10' THEN 'Straight Truck'
        ELSE 'Invalid'
       END
FROM [dbo].[kansiris];