Curtis Weston's 85th-minute volley kept Gillingham's 11-game unbeaten home league record intact and denied the League Two leaders all three points.
The Chairboys went ahead on 31 minutes when a mix-up saw Stuart Lewis score an own goal after keeper Simon Royce fired his clearance straight into him.
Dennis Oli had a header deflected inches wide as the home team rallied.
Weston struck the equaliser with a 20-yard volley into the top corner as the Gills claimed a deserved point.
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