Invalid source table in Table Operator TTL

[snork-alt]

This statement:

    SELECT
      PULocationID, DOLocationID,
      pu_zones.Zone as PULocationName,
      do_zones.Zone as DOLocationName,
      AVG(fare_amount) as avg_amount
    INTO avg_fares
    FROM TTL(TUMBLE(trips, tpep_pickup_datetime, '1 HOUR'), window_end, '1 HOUR')
    INNER JOIN zones pu_zones ON trips.PULocationID = pu_zones.LocationID
    INNER JOIN zones do_zones ON trips.DOLocationID = do_zones.LocationID
    WHERE PULocationID = 123
    GROUP BY PULocationID, DOLocationID;

generates the above error