With the visitors looking the more likely winners, the midfielder, on loan from Nottingham Forest, unleashed a spectacular 25-yard shot with his right foot that ripped into the top corner of the net.
Sam Baldock had broken the deadlock for the hosts after 27 minutes, chesting down a precise chip forward from Wade Elliott and hammering a sweetly struck right-footed volley past Stuart Nelson from 15 yards for his 18th goal of the season.
But Gillingham improved after the break and deservedly equalised in the 65th minute when Ade Akinfenwa headed back across goal from a right-wing corner and substitute Charlie Lee blasted home from close range.
City made a bright start, which saw Bobby Reid just fail to connect with a Baldock cut-back and Jay Emmanuel-Thomas fail by inches to slide in and convert Reid's cross.
Gillingham found it hard to create first-half chances. Their best effort was a low drive from Bradley Dack, comfortably saved by Frank Fielding.