Bayern Munich coach Louis van Gaal warned Daniel van Buyten of repeating his error against Borussia Dortmund, ahead of Wednesday's Champions League clash with Fiorentina. Even though Bayern won 3-1, Van Buyten's mistake allowed Egypt forward Mohamed Zidan to score the only goal against Van Gaal's side but the Dutch coach sees no room for errors in the Champions League. "Daniel knows he made a mistake. I would rather warn him today before Wednesday," Van Gaal was quoted by German media. Bayern has been in superb form in the Bundesliga since November, amassing maximum points from their last nine games.