UFC confirmed the agreement.
Aldo, winner of 14 straight, including five defenses of the Zuffa-promoted 145-pound title, originally was scheduled to face Koch this weekend in Calgary. However, the 25-year-old Brazilian was forced to withdraw due to a leg injury.
Aldo last fought in January, scoring a first-round stoppage of Chad Mendes in the same building he will entertain Koch.
Koch, 23, steps into the title fight with a 13-1 record. The lanky American has won four in a row after suffering the lone defeat of his career to Mendes in 2010. By the time he steps into the cage with Aldo (21-1), Koch will have been out of action for 13 months.