SLIDESHOW: Bury v Chesterfield in pictures
A late Tom Pope header for Bury condemed Spireites to a 2-1 defeat at Gigg Lane.
Zeli Ismail volleyed the Shakers into a 42nd-minute lead, only for summer signing Kristian Dennis to equalise three minutes later with his first league goal for the Spireites.
But after an even second half, Pope headed home late on to condemn Chesterfield to their third defeat from five away games in League One.