Two goals in the space of 60 seconds ended King’s Lynn Town’s resistance.
The Linnets had led through Sonny Carey’s first-half free-kick.
But promotion-chasing Chesterfield laid siege to the Linnets goal for long periods of the second half.
Lynn – with striker Michael Gash on emergency duties after the departure of centre-half Kyle Callan-McFadden 10 minutes before the break – looked to be holding out as the visitors peppered their penalty area.
But two visiting subs turned the game on its head.
Nathan Tyson got the equaliser on 76 minutes and Tom Whelan added a second before Lynn could even think about regrouping.
It was tough on a Linnets team who fielded another new face, midfielder Alex Babos, while striker Kairo Mitchell watched from the stands, having agreed to join Chesterfield in a deal which is expected to be concluded on Monday.
King's Lynn Town: Richardson, Howard, Fleming, Callan-McFadden (Jackson 35), Denton, Coleman, King (Payne 60), Babos (Kiwomya 81), Carey, Gyasi, Gash. Subs not used: Tsaguim, Gascoigne.
Chesterfield: Smith, Carline, Kerr, Gunning, Maguire, Whittle, Smith (Whelan 56), Weston, Mandeville (Clarke 67), Yussuf (Tyson 56), Asante. Subs not used: Yarney, Dinanga.
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