Tickets for both shows of ''The Prismatic World Tour'' go on sale Mon. Jan., 27, at 10 a.m.
The second show was squeezed because of an overwhelming demand for Katy Perry tickets.
Perry will be touring in support of PRISM, which debuted at number one on The Billboard 200 and remains in the Top Ten three months after release.
The platinum album has given Katy her biggest ever single with "Roar", while "Dark Horse" just became her lucky 13th Top Ten hit on The Billboard Hot 100.
Tickets can be purchased at United Center's box office.