A Russian spacewalk outside the International Space Station ended hours earlier than planned on Wednesday after a cosmonaut discovered an electrical issue with his spacesuit, US and Russian officials said.

Oleg Artemyev was roughly two hours into a six-hour spacewalk when voltage levels in his spacesuit’s battery began to unexpectedly drop, prompting flight controllers in Moscow to repeatedly order the cosmonaut’s immediate return to the space station’s airlock.

“Oleg, drop everything and go back,” a flight controller urged Artemyev from mission control in Moscow, as heard on a live feed of space-to-ground audio. “Drop everything and start going back right away… Go back and connect to station power.”

Artemyev returned to the airlock and connected his suit to the space station’s power.

The flight controller warned Artemyev that he risked losing power to his suit’s oxygen pump, and contact with mission control, if he did not immediately return to the airlock for power. NASA spokesman Rob Navias said Artemyev “was never in any danger.”

Russian flight controllers opted to call off the spacewalk early once Denis Matveev, the other cosmonaut performing the spacewalk, gathered his tools and positioned the robotic arm they had been upgrading back into its normal position. Upon Matveev’s return, the spacewalk ended after 4 hours, at 1:54 p.m. ET (1754 GMT).

The space station, a football field-sized research laboratory in low-Earth orbit, has housed international crews of astronauts for more than two decades, with Russia, the United States, Japan, Canada and the European Space Agency counted as the laboratory’s primary users.

Wednesday’s spacewalk, the 252nd in the station’s history, was planned to install cameras and make adjustments to a European robotic arm affixed to Russia’s Nauka research module that will be used to remotely move equipment outside of the station.