As President Donald Trump and Elon Musk argued on social media on Thursday, the world’s richest man threatened to decommission a space capsule used to take astronauts and supplies to the International Space Station (ISS).

After Trump threatened to cut government contracts given to Musk’s SpaceX rocket company and his Starlink internet satellite services, Musk responded via X that SpaceX “will begin decommissioning its Dragon spacecraft immediately.”

It’s unclear how serious Musk’s threat was. But the capsule, developed with the help of government contracts, is an important part of keeping the space station running.