A Japanese astronaut is worried that a space-induced growth spurt aboard the International Space Station might leave him stranded there.

While it’s normal for astronauts to gain a few inches in height in low gravity, Japan’s Norishige Kanai says he’s grown more than three inches since getting to the ISS only three weeks ago. On Monday night, Kanai tweeted out his concern that he might not be able to fit in the Russian spacecraft that set to bring him back to Earth in June.

“In just three weeks, I just grew like a weed,” Kanai said on Twitter. “This hasn’t happened since I was in high school.”

Growth spurts are standard in space. Without gravity pressing down, bodies tend to lengthen as space expands between vertebrae. But astronauts tend to grow only about an inch or two during a space mission. NASA astronaut Scott Kelly grew nearly two inches after his record 340 days in space. And it’s standard to shrink back once the body is again subject to Earth’s gravity.

The Soyuz spacecraft, the Russian vessel that ferries people and supplies to and from the ISS, has a height limit, and if Kanai gets too tall, he might not fit in it. The ship can carry three people to and from the ISS.

Fortunately for Kanai, that height limit was increased to 6’ 3’’ with the current version of the Soyuz TMA capsule, which the U.S. relies on to ferry astronauts to the ISS. The height limit on the prior capsule, retired in 2003, was 6 feet.

No word on how tall Kanai was when he left — or how tall he is now. But NASA stressed that they weren’t terribly concerned about Kanai’s ability to get back home.

“If he were really concerned about getting taller, he could do some more exercise on the ARED, advanced resistive exercise device on station would help compress his body again,” Stephanie Schierholz, acting NASA Press Secretary, told VICE News. “Getting into his spacesuit to get into the Soyuz vehicle — that action alone would probably compress his spine sufficiently.”