Chesterfield have been charged by the Football Association for fielding an ineligible player in their FA Cup second-round tie against MK Dons.
The Spireites had claimed a 1-0 victory to book their place in the third round, but on-loan Wolves defender Georg Margreitter did not have written permission from his parent club.
They have been drawn to play against either Scunthorpe or Worcester City in the next round, but their place is now under threat.
"We had a verbal agreement to play Georg but unfortunately we did not ensure that the consent was received in writing," Chesterfield executive Chris Turner is quoted as saying by BBC Sport.
"We will of course provide the FA with our full co-operation as they investigate the matter."
Chesterfield will have until 5pm on Thursday, December 11 to reply to the charge.
