Warren Buffett’s buy-and-hold strategy doesn’t always work out, as his Berkshire Hathaway Inc. is taking a bath Friday on its big investment in Kraft Heinz Inc., after the packaged food company reported disappointing results, slashed its dividend and disclosed an SEC investigation.

And that’s also bad news for Berkshire Hathaway investors.

Kraft Heinz’s stock KHC, -1.41% plummeted 28.0% toward a record low in active afternoon trade, enough to make it the worst performer in the consumer staples sector XLP, +0.58% and the S&P 500 index. SPX, +1.05% That would be the stock’s biggest ever one-day decline, by far, since the company was spun out of what is now Mondelez International Inc. MDLZ, -0.07% in 2012.

The company had reported last Thursday fourth-quarter earnings and revenue that missed expectations and cut its dividend by 36%. If that’s not bad enough, it received a subpoena from the Securities and Exchange Commission, resulting from an investigation into the company’s accounting. Read more about Kraft Heinz’s Q4 results, and Q3 results.

Now the bad news for Buffett.

Berkshire Hathaway owned 325,634,818 shares of Kraft Heinz as of Dec. 31, according to the latest 13-F filing with the Securities and Exchange Commission. That represented about 26.7% of the shares outstanding, while the value of the holding was just under 8% of Berkshire’s total equity holdings.

If Berkshire’s stake remained intact, it would be worth about $4.4 billion less than it was the day before.

It’s no wonder Berkshire’s Class B shares slumped 1.6% Friday, to pace the financial XLF, -0.83% losers.

Berkshire’s stake in Kraft Heinz has been the same since the third quarter of 2015, according to SEC filings. Before that, filings showed ownership of just 192,666 shares of Kraft Foods Group Inc. and 578,000 shares of Mondelez.

Since Sept. 30, 2015, the stock has now plummeted 50.9%. That indicates Berkshire’s investment has lost $11.7 billion in principal value since then, including an $11.3 billion loss in 2018 alone.

Now the bad news for Berkshire shareholders, the loss on Kraft’s investment could impact Berkshire’s earnings.

Berkshire’s 10-K filing for 2017 details its investments in H.J. Heinz Holding Corp., which eventually became its holding of Kraft Heinz (page 76). Based on the equity method of accounting, Berkshire determined the earnings for its investment in Kraft common stock were $2.9 billion in 2017. The company said it received $797 million in dividends on the stock during 2017, down from $952 million in 2016.

See related: Kraft, Heinz agree to merge in Buffett-backed deal.

Barclays analyst Jay Gelb cut his fourth-quarter operating earnings per share estimate on Berkshire’s Class B shares to $1.15 from $2.35 as a result of its Kraft Heinz holdings. He reiterated his neutral rating and $250 stock price target.

Buffett’s annual letter to shareholders is expected to be revealed on Saturday, as Berkshire reports fourth-quarter results and files its 10-K for 2018.

The result of Berkshire’s aggressive bet on Kraft Heinz seems to run counter with the defensive nature of being a consumer staple, which provide goods and services that consumers see has daily needs rather than wants.

See also from Barron’s: Kraft and other packaged-food stocks aren’t a safe haven anymore, analyst says.

Meanwhile, prior to Friday’s debacle, Kraft Heinz’s stock had lost 28.6% over the past 12 months, while the SPDR Consumer Staples Select Sector exchange-traded fund had gained 1.9% and the S&P 500 index had advanced 2.7%. Berkshire shares rose 2.1% over the same time.