Matthew Warner hit the only goal after 25 minutes as the Conference South's bottom side Basingstoke earned a shock win at Carling Cup heroes Chesterfield.
Chesterfield have beaten Manchester City and West Ham in the cup but were deservedly beaten at Saltergate.
Visiting keeper Stuart Searle made blocks from Caleb Folan and Mark Hughes but there were few other scares.
In fact James Taylor could have made it two before losing control when clear, but Basingstoke held on for the win.
Chesterfield: Roche, Lowry, Kovacs, Downes, O'Hare, Hall (Jackson 69), Niven, Hughes (Davies 83), Smith, Allison, Larkin (Folan 58).
Subs Not Used: Nicholson, Hazell.
Basingstoke: Searle, Watkins, Wells, Dolan, Bruce, Ray, Surey, Taylor, Warner, Cristian Levis (Roach 66), Stroud.
Subs Not Used: Howell, McKay, Bristow, Quarm.
Goals: Warner 25.
Ref: G Ward (Kent).