Union Berlin came from behind to end Leipzig's unbeaten run as goals from Janik Haberer and Robin Knoche ensured a 2-1 away win in the 20th round of Bundesliga on Saturday.
Leipzig started powerfully on home soil and dominated possession in the opening stage against the defensively-minded Union.
The Red Bulls didn't produce a lot of chances, but still were able to break the deadlock with 24 minutes gone when Benjamin Henrichs' long-range effort caught Union goalkeeper Frederik Ronnow flat-footed.
The visitors from the capital lacked penetration, and had to wait until the 38th minute when Sheraldo Becker forced Leipzig custodian Janis Blaswich from a tight angle.
After the break, Union assumed control as Blaswich had to be on guard to defuse Josip Juranovic's header on target, before Haberer volleyed home a miscued clearance.
Things went from bad to worse for the hosts as Mohamed Simakan handled the ball inside the box.