Luke O'Nien's superb finish proved the difference as Wycombe extended their unbeaten run to five games in all competitions with a narrow 1-0 victory over Chesterfield.The Spireites had not lost a League Two match since October 21 - a run of six games - but O'Nien cut inside after 54 minutes and rifled a shot into the far corner to lift Wanderers to fourth in the table.Craig Mackail-Smith had looked certain to give Wycombe the lead after 25 minutes when Joe Jacobson's cross was not properly cleared, but Cameron Dawson somehow made himself big enough to block the forward's fierce point-blank shot and then smothered a tame follow-up effort.Goalkeeper Dawson was helpless when Sam Saunders shaped a stunning free-kick towards the top corner in the final moments of the half but the ball rebounded away from danger after rattling the crossbar.And the Chairboys got the only goal nine minutes after the restart as O'Nien's fine left-footed effort beat Dawson.