The invention relates to a round baler having a bale chamber in which a round bale can be produced, and a wrapping device with which a completely pressed round bale can be wrapped with a first plastic film in the bale chamber, and a feed device for feeding the first plastic film into the bale chamber. The round baler also includes a feed point at which the first plastic film can be fed to the bale chamber, and an ultrasonic sensor which is arranged at the bale chamber. The ultrasonic sensor is arranged at the bale chamber in such a way that with the ultrasonic sensor it is possible to determine whether the first plastic film is present on a surface of the round bale. The invention also relates to a detection method for detecting a first plastic film on a surface of a round bale.
