Blue Square Bet North leaders Alfreton Town were beaten for this first time in eight matches following a 4-2 defeat at Eastwood Town.
The Reds still need five points from their last five matches to secure automatic promotion.
Matt Rhead put the home side ahead after 12 minutes, while Liam Hearn's 27th of the season soon levelled.
Michael Simpson, David Haggerty and Andy Todd made it 4-1, before Ant Wilson's late consolation.
Eastwood, who are now unbeaten in their last 14 league matches, have moved into the play-off places on goal difference.
But they will not be allowed to take part in the Blue Square Bet North play-offs, subject to an appeal, following a Football Conference ruling.