Nissan Motor shares jumped the most in 15 years after the beleaguered automaker revealed an activist investor has taken a 2.5% stake.

The jump is a remarkable turnaround for Nissan’s stock, which plunged last week after the carmaker slashed jobs and said it would cut manufacturing capacity by a fifth.

Nissan also lowered its financial forecasts for this fiscal year.

Nissan’s filing said Suntera (Cayman) is the buyer of the 2.5% stake and listed Suntera as a trustee of ECM Master Fund.

A filing from Sanken Electric from 2021 cites ECM Master Fund as being managed by Effissimo Capital Management, a Singapore-based hedge fund.

Effissimo and Suntera are well-known in Japan for leading a campaign over Toshiba in 2021 that culminated in a buyout of the manufacturer.

Nissan said in a statement that it is "continuously engaging with institutional investors and analysts from securities companies.”

The company added that it’s not in a position to identify whether the stake acquisition was indeed done by Effissimo.

The automaker’s shares climbed as much as 20.6% before paring the gain to about 13%.

Effissimo, set up by former colleagues of an activist investor Yoshiaki Murakami, became Toshiba’s top shareholder in 2017 when the company was reeling from a massive write-down on its nuclear power business.

Representatives for Effissimo didn’t respond to an email seeking comment.

Activist investor campaigns in Japan have become increasingly common over the past decade.

Elliott Investment Management has built sizable stakes in Sumitomo and SoftBank Group, while Oasis Capital earlier this year called for a governance overhaul at Japanese drugstore chain Ain Holdings.

If an activist investor is involved, Nissan’s stock will probably rise further as shareholders speculate the automaker may embark upon structural reforms to fix its ailing business, said Ikuo Mitsui, a fund manager at Aizawa Securities.

Nissan’s short interest stood at 21% of its free float as of Friday, making it the third-most shorted stock on the 225-issue Nikkei stock average, according to data from S&P Global.

Nissan said last week that it now sees its operating income plunging to just ¥150 billion ($976 million) in the fiscal year ending in March, down 70% from its previous forecast.

Management also lowered their revenue outlook by more than 9%, meaning they now expect virtually no growth for the year.

Chief Executive Officer Makoto Uchida told investors that Nissan has been affected "not only by external challenges, but also by our specific issues,” alluding both to the breakneck rise of Chinese automakers and Nissan setting overly ambitious sales targets.