Midfielder Jimmy Ryan has had his contract with Chesterfield extended until the summer of 2015.
Ryan's appearance in the Spireites' 4-0 victory over Bury on Saturday triggered a 12-month extension clause in his agreement.
And Blues boss Paul Cook is pleased to have secured the 25-year-old to a longer deal.
He said: "We are all delighted with Jimmy's contribution and I know he's very happy here so I think it's a perfect fit."
Ryan, who has scored two goals in 26 league and cup appearances this season, signed for Chesterfield after coming to the end of his contract at Scunthorpe. He previously played for Accrington and Shrewsbury after being at Liverpool as a youngster.
Meanwhile, Cook has thanked Gary McSheffrey for the contribution he made during a four-month stint at the Proact Stadium after deciding against offering the forward an extended deal.
"I'd like to thank Gary for his services and wish him well for the future," said Cook.
McSheffrey, who scored two goals in 12 appearances for the Spireites, has subsequently signed for League Two promotion rivals Scunthorpe.