Python pygame queue function does not play queued song

Question

Hello so I am trying to build a small MP3 player with pygame and everything works fine, except the queue function from the pygame module. When I play a song and queue the next one, the next one will not be played. I am using Tkinter for the GUI.

def playBack(self):
            global current, playlist
            mixer.music.load(playlist[current])
            mixer.music.play()
            mixer.music.queue(playlist[current+1])  

I would be thankful if anybody could help me solve this as I am new to the pygame module.