There are several different factors that help to determine how tall each of us stands. Genetics obviously plays a big role, but the gravitational pull of the Earth also has a say in the matter, and Japanese astronaut Norishige Kanai just discovered that the planet has been making him several inches shorter.

Kanai, who only just arrived at the International Space Station on December 19th, took to Twitter to announce that his brief stay in space has resulted in a growth spurt of nine centimeters, or about three and a half inches.

“Good morning, everyone,” Kanai wrote. “Today I share some serious news. Since coming to space, I have grown 9 centimeters. This is the most I’ve grown in 3 weeks since junior high school.”

Scientists have long known that the lack of gravity in space leads to temporary jumps in height, but the typical change is around two inches. Kanai has already grown nearly double that, and while it might sound like a pleasant side effect of a trip into Earth’s orbit, it can have some very real consequences.

Most of the vital equipment each astronaut brings with them is custom made — space suits aren’t exactly a “one size fits all” item — and a change of nearly four inches could make things feel a wee bit cramped for Kanai. “I’m a bit worried whether I’ll fit in the Soyuz sea when I go back,” Kanai said, though that’s a bit of a humorous exaggeration.

The Japanese space traveler’s height gains will be short lived, however, as his planned return to Earth later this year will result in his body compressing back down to his normal height.

UPDATE: Kanai had apparently intended his comments has a joke, and has since apologized for spreading “fake news.”