The first flight of NASA’s next big rocket, the Space Launch System, likely won’t launch until June 2020, though it’s now officially scheduled to get off the ground sometime in December 2019, according to the space agency. The new official date marks a one-year delay for the monster vehicle that’s meant to take astronauts into deep space.

These new dates are the result of a “comprehensive review” by NASA looking into the rocket’s schedule. Ultimately, the review found that a launch in June 2020 would be more reasonable, based on risks that might arise during manufacturing and production schedules. But NASA is working toward a December 2019 date, since none of the risks the agency identified have arisen yet, according to NASA acting administrator Robert Lightfoot.

In April, NASA finally admitted its then-target date, November 2018, just wasn’t going to work

NASA made it clear earlier this year that the SLS’s first flight, an uncrewed mission called EM-1, would be pushed back. In April, the space agency finally admitted that its then-target date for the launch, November 2018, just wasn’t going to work. The admission came after a government audit found that technical challenges and a limited budget would make a November 2018 date nearly impossible.

Although the SLS’s first flight is delayed a few years, a test for the Orion capsule meant to ride on the rocket has been accelerated. The Orion capsule is meant to carry crew — and before the Orion actually holds any people, NASA wants to conduct a test of the vehicle’s emergency system to protect crew if the rocket malfunctions during launch. This system, called the launch abort system, consists of a tiny rocket that can carry Orion away from the SLS. Originally, the test of the abort system was going to happen after EM-1, but NASA is moving it up to April 2019.

This isn’t the first review NASA has done this year regarding the debut of the SLS. Earlier this year, the Trump administration asked NASA to figure out whether astronauts could fly on the first mission of the SLS. For the last few years, the strategy has been to roll out the giant rocket by doing an uncrewed mission first, followed by a crewed one a few years later. NASA did a study to see if a crewed mission could be done safely by 2019, without the need for a crewed mission, but the report ultimately found it would be too difficult for NASA to pull off in such a short time.