(CNN) -- Early Bundesliga leaders Mainz underlined the seriousness of their title challenge with a 2-1 win at the Allianz Arena stadium of defending champions Bayern Munich on Saturday.
It leaves them top of the table with six wins from six, three points clear of second-placed Borussia Dortmund and 10 clear of faltering Bayern, who are eighth.
Mainz made a dream start and took the lead after 15 minutes as Lewis Holtby crossed for Tunisian international Sami Allagui to score with an impudent backheel.
Bayern were clearly missing the influence of injured Franck Ribery but drew level just before halftime when Mainz defender Bo Svensson headed past his own goalkeeper.
But Mainz kept their composure and shocked Bayern with a 77th minute winner through Adam Szalai.
"We didn't play well. It was all due to Mainz, we just didn't create enough chances," Bayern manager Louis van Gaal told AFP.
Dortmund maintained their fine start to the German season with a 3-1 win over St. Pauli as Kevin Grosskreutz scored twice.
Schalke 04 owed their 2-2 home draw Borussia Moenchengladbach to a late equalizer from their former Real Madrid star Raul, his first for his new club.
It took them off the bottom of the table at the expense of Stuttgart, who were thrashed 4-1 at home to Bayer Leverkusen, who are fourth.
High-flying Mainz will face third placed Hoffenheim next week knowing that victory will see them equal the record of seven straight wins from the start of the Bundesliga season, jointly held by Kaiserslautern in 2001-2002 and Bayern Munich in 1995-96.