Legalized sports betting is giving a boost to Boston-based DraftKings’ Back Bay office footprint.

The fantasy sports betting website moved to a 105K SF headquarters at 500 Boylston St. in March, and the company is already planning a 20K SF expansion. The current headquarters is on the fifth floor of 500 Boylston, while the new section will be on the fourth floor of the adjoining 222 Berkeley St.

DraftKings is expected to move into the new office by Q3 or Q4 of 2020, the Boston Business Journal reports. Oxford Properties owns both buildings.

Graham Walters, the chief people officer for DraftKings, told the BBJ the expansion is driven by more states legalizing sports betting.

The company already operates sports betting in four states and has plans for three more — Pennsylvania, Iowa and Indiana. Lawmakers in DraftKings' home state of Massachusetts are still considering legalizing the form of gambling.

Along with the traditional office expansion, DraftKings signed a five-year, 100-desk lease in June at Tishman Speyer’s Studio coworking concept at 125 High St. While the company didn’t say which teams would be based at the downtown Boston Studio office, it also attributed that growth to legalized sports betting.