Town boss Nathan Jones was left frustrated as his side slipped to a 2-1 defeat at the ABAX Stadium in the Checkatrade Trophy this evening.
Having already qualified in top spot, the Hatters fell behind in the 19th minute from Colin Daniel's low effort, before Ivan Toney curled in a free-kick with nine minutes of the first half left.
Conor O'Malley fumbled Matty Pearson's cross into the back of his own net with just under 20 minutes left to play in the second half, but the Hatters were unable to find a late equaliser.
Jones said: "It felt like déjà vu, like the league game here really. First half we were nowhere near, absolutely nowhere near. We played like a team that had already qualified.
"Then second half I thought we were excellent and could have got something from the game. But, once again you're chasing the game – you're 3-0 down in the league game and you don't know how it happened. Naïve defending, there wasn't enough intensity and today was exactly the same. Second half when we played like we actually can play, we were the better side. It's frustrating.
"There wasn't that real zest, we didn't get first contact from corners, we didn't have the zest to go out and win the game. We did start a lot better than them, but then the goal came, we let them press and do what they want, we made them look a good side in the first half in two games now.
"Second half we upped the tempo, we played structurally, we looked a better side, but we have to chase the game again."