The U.S. Supreme Court on Friday agreed to temporarily block the execution of Oklahoma prisoner Richard Glossip later this month after an “unprecedented” request from the state’s attorney general to do so.

In an unsigned order, the court agreed to “stay” the execution of Glossip until the justices decide whether to hear his appeal to overturn his conviction and death sentence for a 1997 murder. If the court ultimately declines to hear the case, the stay will lift and Glossip’s execution will proceed.