Peter Vincenti scored from the penalty spot as League One Rochdale knocked Championship outfit Nottingham Forest out of the FA Cup at the Spotland.
Dale were awarded the spot-kick after defender Joe Rafferty was tripped by Forest winger Michail Antonio and forward Vincenti duly converted.
The visitors had chances to equalise in the second half but could not find a way past Dale goalkeeper Josh Lillis.
Forest have now won just twice in their last 18 games in all competitions.
And a defeat by a team in a division below them in this third-round tie has put further pressure on Forest manager Stuart Pearce.