Mainz handed Bayern Munich their first home defeat of the Bundesliga season as they claimed an excellent 2-1 victory at the Allianz Arena on Wednesday.
The visitors took an unlikely lead against the run of play midway through the first half when Jairo Samperio finished off an excellent break.
Arjen Robben eventually found an equaliser just after the hour, but Jhon Cordoba then re-established Mainz's lead four minutes from time with an excellent finish.
With second-placed Borussia Dortmund winning at Darmstadt on Wednesday, Bayern's lead at the top of the table has now been cut to five points ahead of Saturday's Der Klassiker at Signal Iduna Park.