Charlton ruined the party at Rotherham and put a dent in the Millers’ promotion hopes with a 1-0 victory.
The recently won Papa John's Trophy was paraded before the match but the mood was killed by George Dobson's second-half winner.
Defeat leaves Rotherham three points outside of the automatic promotion berths they have occupied for a large part of the season.
Ben Wiles threatened early on for Rotherham with his long-range volley whistling just wide of the post.
Conor Washington snuck through on goal for the visitors but was denied a shot on goal thanks to a great recovering tackle by Ollie Rathbone.
Viktor Johansson had to get in the way of Washington's lobbed effort early in the second half but there was nothing he could do to stop them taking the lead on 55 minutes.
Neat interplay around the box saw Dobson teed up and the midfielder rifled an unstoppable shot into the corner.
Rotherham's best chance to level fell to substitute Mickel Miller but he fired over from close-range.