League One leaders Southend blew the chance to move 11 points clear after losing to Gillingham.
An expectant Roots Hall crowd were looking for Southend to move closer to promotion.
However, the visitors from Kent had other ideas as they clinched victory.
The only goal came just after the interval when Tommy Black struck from the edge of the box after good work from Matthew Jarvis.
The win sees Gillingham move up to tenth, but a push for the play-offs looks just beyond them.
In the day's other game, Scunthorpe beat Yeovil 1-0 at Huish Park courtesy of Billy Sharp's strike on 57 minutes.
While the result kills off any lingering fears of relegation for The Iron, Yeovil remain just four points clear of the drop zone and, having played one more game than their rivals, they will be looking over their shoulders this weekend.