Williams has appointed Adrian Sutil as its reserve Formula 1 driver for 2015.
The German has been out of work since being dropped by Sauber at the end of last season.
In the wake of Valtteri Bottas's absence from the Australian Grand Prix, there was uncertainty about who Williams would use in the event of one of its regulars being unable to race.
It has Susie Wolff on its books as a test driver and GP3 champion Alex Lynn as a development driver, but neither was in an official 'reserve' role.
But in a deal announced in Malaysia on Thursday, Sutil will now be drafted in if required.
He is due to spend time in the team's simulator to fully get up to speed with the performance of its 2015 challenger.
"I'm very proud to be a part of such a famous and great F1 team," said Sutil.
"To work for Sir Frank Williams and his team means a lot to me.
"I would like to thank everyone at Williams for their belief in my qualities and the opportunity to work with such a successful and competitive outfit."
Team boss Frank Williams said getting a driver with recent race experience as a reserve was essential for his outfit, as it faces a tough battle behind Mercedes this year.
"The fight for a top constructors' championship position will be intense this season, therefore we have selected a driver with recent race experience and are confident that if the need arose, he would be a solid pair of hands to race the FW37 and assist our 2015 campaign," Williams explained.
Sutil made his F1 debut with Spyker in 2007, and stayed with the outfit under its Force India moniker until '11.
After a year out in 2012, he returned to the team in '13 before the switch to Sauber for the following campaign.
THE 2015 F1 SUBS BENCH