"Streaming of ' on this platform is not supported" even when not streaming

I'm trying to download a mp3 file in a coroutine like this:

      IEnumerator Download(SongResult song) {
       Debug.Log ("Starting download for song");
       Debug.Log (song.PreviewURL);
       WWW www = new WWW(song.PreviewURL);
       yield return www;
       song.PreviewAudio = www.GetAudioClip(false,false,AudioType.MPEG);
       }

The urls look like this: https://p.scdn.co/mp3-preview/bc7164c65a4be27009db16dc8bbddbd61a41ac9b

I don't want to stream the file so I'm passing false for the streaming parameter but Unity does complain as follows:

 Streaming of '' on this platform is not supported

What am I doing wrong?

Best regards,

Chris