Seems there is conflict in Tim Peake's schedule.
The British astronaut would like to run the London Marathon, but he will be almost 250 miles above the Earth's surface on race day.
So Peake is hoping to complete a virtual marathon -- on a treadmill, with video of the London course playing before him -- in the International Space Station.
"The London Marathon is a worldwide event," he said on a video promoting his effort. "Let's take it out of this world."
This won't be the first time someone has attempted to run 26.2 miles in orbit. NASA astronaut Sunita Williams did it during the 2007 Boston Marathon.
The 43-year-old Peake competed in cross-country when he was younger and previously completed the London Marathon -- on Earth -- in 1999. This time, he will have to wear a harness.
"In micro-gravity, I would float if I didn't strap myself down," he said. "After about 40 minutes to an hour, that gets very uncomfortable."