At least one shareholder of Alleghany Corp. is unhappy with the insurer’s agreement to be bought by Warren Buffett’s Berkshire Hathaway.

According to a lawsuit filed April 13 in U.S. District Court for the Southern District of New York, shareholder Shiva Stein said Alleghany and its board of directors failed to explain in a proxy statement why shareholders should vote in favor of the acquisition.

Alleghany has asked its investors “to support the proposed transaction based upon the materially incomplete and misleading representations and information contained in the proxy statement,” according to court documents. Alleghany’s board has voted to approve the transaction.

The analyses by Alleghany’s financial adviser, Goldman Sachs, in support of its “fairness opinion” is specifically incomplete and misleading, alleged Stein, who seeks to prohibit the acquisition by Berkshire until the right information is given to shareholders or to recover damages resulting from Alleghany’s alleged violations of the Securities Exchange Act of 1934. The proxy statement, filed April 11, “fails to provide material information concerning financial projections by Alleghany management and relied upon by Goldman Sachs in its analyses,” the suit said.

A report about a year ago from Reuters said Stein is no stranger to securities litigation. According to legal data analytics company Lex Machina, she was one of the “most prolific” securities plaintiffs in the United States, filing 124 securities suits between 2018 and 2020.

Most recently, Stein filed a similar lawsuit to stop Google’s $5.4 billion deal to buy Mandiant, according to reports.

Stein in June 2020 filed litigation as an individual shareholder and made similar allegations regarding incomplete or misleading proxy statements following the proposed Aon acquisition of Willis Towers Watson (since rebranded as WTW).

Goldman Sachs was involved as financial adviser of each deal but in each lawsuit brought by Stein, Goldman Sachs was not named as a defendant.

However, Goldman Sachs has been a target of Stein. She sued the bank in 2017 over a stock-incentive plan for managers and directors, which Stein alleged was not properly outlined to shareholders.