Tom Naylor dumped his old club Portsmouth out of the FA Cup as Chesterfield won their first-round tie 1-0 at the SMH Group Stadium.
Former Pompey midfielder Naylor headed home in the first half as the National League leaders defeated opponents who hold the same position in the League One table.
Ollie Banks forced Will Norris into the first save and then curled a shot just wide as the Spireites started well.
Portsmouth’s Paddy Lane shot at the near post but Harry Tyrer saved low to his left at the expense of a corner.
Chesterfield claimed a deserved lead just after the half hour as Liam Mandeville curled in a free-kick and Naylor beat Norris to the ball to head home.
Colby Bishop’s downward header was too close to Tyrer as the home side comfortably held their lead to the break.
Banks shot at Norris early in the second half and Armando Dobra twice saw penalty appeals denied as Chesterfield continued to dominate with an hour gone.
Portsmouth substitute Abu Kamara headed wide as the visitors looked for a way back into the tie.
But Paul Cook’s side had done enough to reach round two.