Luton boss Joe Kinnear laid the blame for this defeat at the door of goalkeeper Carl Emberson.
Kinnear put Chesterfield's 59th minute winner down to an own goal although David Reeves was given the credit.
Kinnear said: "Although they've given it to Reeves, if you look on the video it's an own goal, the keeper punched it into the net." Kinnear was also critical of his team's defending when Glynn Hurst put Chesterfield level four minutes earlier.
Luton should have taken all three points but poor finishing and errors at the back proved costly.
Ben Williams marked his first league appearance in the Chesterfield goal by conceding a soft goal when he missed an in-swinging corner from Ahmet Brkovic after only eight minutes.
But Williams, on a month's loan from Manchester United, recovered well and saved from Tony Thorpe and made another crucial block to deny the experienced striker in the 54th minute.
That was a turning point because a minute later Hurst raced away to scored with a low shot after Emerson Boyce had needlessly given the ball away.
Chesterfield's winner was a soft goal, with Emberson flapping at a Reeves header that appeared to drop over him and into the net.
Luton forced a string of corners but Chesterfield defended well and Hurst almost scored a third in injury time.