Berkshire Hathaway (BRK.A, $304,057) Loses Nearly $4 Billion Today, As Apple (AAPL, $157.92) Shares Fall -9%

Warren Buffett may just have lost $4 billion – as Apple shares took a hit following a downward revision in  expected sales.

Holding about 252.5 million shares of Apple, Buffett's Berkshire Hathaway is the iPhone maker’s second-largest investor.

Last August, Buffett told CNBC that he was not too concerned about iPhone "sales in the next quarter or the next year", compared to the fact that there are "hundreds millions of people who practically live their lives" by the iPhone – a reason why he was so fond of the company. Buffett also felt that the iPhone was "enormously underpriced". Berkshire began investing in Apple in early 2016.

According to a letter from Apple CEO Tim Cook on Wednesday, Apple might experience lower sales from the holiday quarter than what was possibly expected. Lower- than-expected iPhone sales in China amidst ongoing trade tensions with the U.S. coupled with other factors like the company offering cheaper iPhone battery replacements were mentioned as factors behind the dampened sales expectations.

Apple makes up 25.7% of Berkshire's total portfolio.  Berkshire shares fell more than -4% while Apple’s stock price plunged  -9% Thursday morning.

Other major investors of Apple include Vanguard (the largest owner of Apple), BlackRock, State Street and Fidelity.