The failure of software responsible for the automatic docking of Russian cargo spacecraft Progress M-21M has resulted in the unexpected upside of saving time and fuel, the Energy Rocket-Space Corporation said Monday.

"After an alarm signal came out (during the docking), we switched to the manual mode of approaching and found out that we've saved about 200 kg of fuel," Energy's president Vitaly Lopota was quoted by the Interfax news agency as saying.

The manual docking, operated by Russian cosmonaut Oleg Kotov, also completed the process 10 minutes ahead of schedule.

The Progress M-21M, launched on Nov. 25 by a Soyuz-U rocket to resupply six ISS crew members with 2.4 tons of cargo, docked at Russia's Zvezda module of the International Space Station on Saturday.

This is the second time the Kurs-NA docking software has failed, after a problem in 2012. This time, the system failed just 60 meters before docking.

Lopota said tests of the Kurs system would continue.