They held firm at FC Halifax to set up a final four tie at Solihull Moors on Sunday.
Danny Rowe headed the visitors in front before Jeff King, pictured, stunned his old club with a sensational strike.
Matt Stenson quickly responded but it couldn’t provoke a comeback and the Spireites go through to the joy of over 2,000 travelling fans.
Paul Cook says he never questioned his players once despite a dreadful final few months of the season.
He told us: “We just about limped over the line to get into the play-offs but I knew we had the character.
“It was the total opposite to what we have been for a while.
“We looked like a team - and we looked like we had the desire to go and win.
“It was a great performance to come to a team who are so strong at home, the players were fantastic.”