Chesterfield maintained their unbeaten start to the season to go top of League Two, but were given a fright by Bury.
The hosts dominated proceedings and deservedly led through Steve Fletcher's first-half goal when he headed in Peter Leven's cross from the left wing.
With 15 minutes left Colin Woodthorpe headed Bury back on level terms, but that only stung Chesterfield into life.
Fletcher scored a second header from Jamie Lowry's cross and Jack Lester's crisp finish wrapped up the victory.
Chesterfield: Roche, Picken, Robertson, Gray, Kovacs, Lowry, Niven, Leven, Algar (O'Hare 85), Fletcher, Lester.
Subs Not Used: Jordan, Allison, Law, Jackson.
Goals: Fletcher 33, 77, Lester 84.
Bury: Provett, Parrish, Morgan, Challinor, Futcher, Scott, Woodthorpe, Dean (Mangan 60), Barry-Murphy, Bishop, Adams (Dorney 83).
Subs Not Used: Haslam, Rouse, Baker.
Booked: Futcher, Scott, Challinor.
Goals: Mangan 75.
Ref: Gavin Ward (Surrey).