High-flying Chesterfield's unbeaten away record vanished at Notts County thanks to Stephen Hunt's header.
The Magpies defender was left unmarked to place the ball into the bottom corner from Neil MacKenzie's free-kick.
The Spirietes dominated the first half and created a host of chances with striker Jack Lester going close on three separate occasions.
County improved after the interval and substitute Andy Parkinson could have wrapped things up with a late volley.
Notts County: Pilkington, Canoville, Tann, Hunt, Mayo, Somner, MacKenzie (Silk 79), Butcher, Sam (Dudfield 53), Lee, Weir-Daley (Parkinson 68).
Subs Not Used: Sandercombe, McCann.
Booked: Butcher, Dudfield.
Goals: Hunt 21.
Chesterfield: Roche, Picken, Kovacs, Downes, Robertson, Leven, Niven, Winter (Jackson 71), Lowry (Allison 82), Fletcher (Rooney 57), Lester.
Subs Not Used: Gray, O'Hare.
Booked: Winter, Picken, Downes.
Ref: J Moss (England).