The former Lincoln man scored against the Harriers in both games between the sides this term, and will earn the Bulls additional sums based on their final league position this term.
The 25 year old has made a total of 51 Conference appearances for the Bulls, scoring 15 goals.
O'Keefe has signed an 18 month deal.
O'Keefe has signed an 18 month deal.
Meanwhile, the Harriers have let three players go. Midfielder Lee Fowler and wingers Dior Angus and James Dance have all left the club by mutual consent.