Nottingham Forest maintained their late push for the play-offs and stretched their unbeaten run to seven games with a comfortable victory at Saltergate.
Ian Breckin headed their opener after a slip by ex-Forest keeper Barry Roche and Nathan Tyson capitalised on Alex Bailey's mistake to hit the second.
Phil Picken gave Chesterfield hope by pulling one back from 25 yards.
But John Thompson headed in Kris Commons' corner to seal it and inflict Chesterfield's fifth straight defeat.
Chesterfield: Roche, Bailey, Downes, O'Hare, Picken, Allott,
Niven, O'Hara, Larkin, Hall (Hurst 60), Allison (Heath 74).
Subs Not Used: Davies, Foyle, Beckwith.
Goals: Picken 33.
Nottm Forest: Pedersen, Perch, Breckin, Morgan, Curtis,
Clingan (Thompson 84), Gary Holt, Bennett, Commons,
Grant Holt (Lester 72), Tyson.
Subs Not Used: Gardner, Cullip, Gamble.
Booked: Gary Holt.
Goals: Breckin 19, Tyson 29, Thompson 87.
Ref: A Woolmer (Northamptonshire).