Challenging times are on the horizon for South Korea’s future casinos.

Several weeks ago, the Ministry of Culture, Sports and Tourism (MCST) awarded the country’s new integrated resort license to Connecticut tribal casino operator Mohegan Sun, which has partnered with South Korean chemicals maker KCC Corp. for a $5 billion casino resort at the Incheon International Airport.

The consortium, called Inspire Integrated Resort, plans to open the casino’s doors by 2020. But even before the casino operator was able to break ground, a credit rating agency already has a word of warning.

Fitch Ratings Inc believes that South Korea’s new casino “will have difficulty achieving robust returns on investments.” The reason: a government’s rule that will limit the integrated resort to foreigners only.