Astronauts have patched a tiny hole that was allowing air to leak from the Russian side of the International Space Station.
Nasa and Russian space officials stressed the six astronauts were in no danger.
The leak was detected on Wednesday night — possibly after a micro-meteorite strike — resulting in a small loss of cabin pressure.
It was traced to a hole about 2 millimetres across in the most recent Soyuz capsule docked at the space station.
On Thursday morning, the crew taped over the hole, slowing the leak. Flight controllers monitored the cabin pressure while working to come up with a better long-term solution.
The leaking Soyuz — one of two at the station — arrived at the orbiting lab in June with three astronauts.
It will also take them home in December, and serves as a lifeboat in case of an emergency.
A Nasa spokesman said it was too early to speculate on whether the three might have to return to Earth early if the leak cannot be stopped.
The hole is located in the upper section of the Soyuz, which does not return to Earth, according to Nasa.
The 250-mile-high outpost is home to three Americans, two Russians and one German. Orbital debris is a constant threat to spacecraft, even the tiniest specks.