For the third year in succession, Borussia Dortmund supporters will protest against Bundesliga ticket prices by leaving the stands at Hamburg when the match between the two clubs begins.
Two years ago, Borussia fans started the "Kein Zwanni" (No €20 tickets) movement. The campaign against ticket-price hikes by Bundesliga clubs began with a boycott of the local derby against Schalke and, for the first time in years, that match failed to sell out.
The boycott spread, and supporters of other Bundesliga clubs joined in. Two years later, Kein Zwanni, which protests against price rises for both seating and terraced areas, will focus its protests on Hamburg, where the cheapest seat costs €40.
After boycotting the 2010-11 match between the two clubs and listening to the radio commentary outside the stadium, fans now plan to leave the stadium when the first whistle blows.
A Kein Zwanni statement said: "We call on all BVB supporters to join in our protest. An empty away standing area and many vacancies in the seats will not be overlooked by the media.
"Let's increase the pressure on the people in charge together and lend weight to our claim for affordable tickets. We might ask a lot from you - but we hope you join in. United we are strong. Keep football a sport for all people."
Even though prices in Germany remain relatively low compared with those in other leagues in Europe, supporters fear that those on moderate incomes and younger fans could be priced out of attending games. Clubs are aware of the problem and have been in talks with fans' groups.
When asked about the forthcoming protest in Hamburg, Dortmund coach Jurgen Klopp said: "That's going to be like an echo of thunder. There will be no winners. When the away terracing is filled, it can get very loud."
Kein Zwanni spokesperson Christian Scholer told ESPN: "I also think there will be no winners - there would only be winners if Hamburg start moving on prices. The fans who leave the stadium don't like being outside. We want to support our team - after all, that's our job."