Officials announced the bout Wednesday night.
Cormier, won the title when he submitted Anthony Johnson last month. The UFC stripped Jon Jones of the belt after his incident in New Mexico involving an alleged hit-and-run.
After his win, Cormier (16-1) and Bader got into a heated exchange at the post-fight press conference. Both sides appeared content with settling the score in the Octagon, as they were originally set to meet this weekend.
On Twitter, “DC” responded to a post about Bader feeling “salty” over being passed over, stating “I would be very upset!”
Gustafsson (16-3) is coming off a knockout loss to Johnson that dropped him from the role of No. 1 contender. After a tough decision loss to Jones, he rebounded to finish Jimi Manuwa before the loss to Johnson.