On 14 March 2015 McKenzie won his first title by beating Ivan Stupalo at York Hall to win the International masters belt, which made him the mandatory challenger for the Southern area title. On 17 October 2015 McKenzie beat the previously undefeated John McCallum at York Hall. The contest was brought to a halt at the end of the sixth round after McCallum was pulled out by his corner after suffering a badly damaged left eye. This edged McKenzie closer to a shot at the British super-middleweight title.