Halifax stunned Oldham with a 2-1 National League victory in front of 7,964 fans at Boundary Park.
Rob Harker fired the visitors ahead after 31 minutes with a superb long-range strike.
Oldham were level five minutes before the break when Mark Shelton fired home from a corner.
Harker went close against for Halifax before the resulting corner fell to Adam Senior, who scrambled home from close range.
