West Ham were taken to the brink of a Worthington Cup upset but held their nerve through a penalty shoot-out to end Chesterfield's brave challenge.
Although the Premiership side dominated the game, the heroics of goalkeeper Carl Muggleton kept the tie in the balance up until the lottery of the shoot-out.
The player who cracked was Chesterfield striker Mark Allott who saw his spot-kick go wide of David James' right-hand post.
All the West Ham players put away their penalties but it was a relieved Hammers side that celebrated in front of their supporters.
This was always likely to be a difficult tie for the visitors given Chesterfield's excellent form in Nationwide Division Two but Jermain Defoe gave his side an excellent start with a goal in the 13th minute.
Ironically it was a route one ball from Sebastian Schemmel that caught Chesterfield cold and the nippy Defoe was in to place a low right-foot shot past Muggleton.
That appeared to be the signal for the floodgates to open but heroic defending and wasteful West Ham finishing kept the score down.
Seven minutes after the break, a packed Saltergate erupted when West Ham froze expecting an offside flag and substitute Chris Brandon ran through to sidestep James and score.
James almost dropped a cross into his own net six minutes later but Muggleton was as solid as a rock, diving at the feet of Joe Cole in the 73rd minute and then plunging to his right to keep out a swerving drive from Defoe.
West Ham's dominance continued through extra time with Muggleton saving his side again in the 95th minute to deny Paolo Di Canio although he was beaten by a Gary Breen header seconds later which Marcus Ebdon cleared off the line.
Cole headed inches wide of Muggleton's right-hand post in the second period of extra time and the keeper made another marvellous side to deny the England midfielder in the 114th minute.
But he could not keep out West Ham's spot-kicks and the Premiership side squeezed through into the third round with only their second win of the season.
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