Investment bank Goldman Sachs (NYSE:GS) is changing the terms on a large block of warrants owned by Warren Buffett's Berkshire Hathaway (NYSE:BRK-B), the company said in a statement today. The upshot: Berkshire is in line to take an ownership stake in Goldman Sachs rather than cash.

Warrants are similar to call options: They are derivatives that allow the purchaser to buy a certain number of shares in a company for a predetermined price within a certain time period. The warrants owned by Berkshire Hathaway allow the holding company to purchase more than 43 million Goldman Sachs shares at $115 per share any time before Oct. 1, 2013.

At yesterday's per-share closing price of $146.11, Buffett and his company were sitting on more than $1.3 billion in paper gains.

The amendment to those warrants today means that instead of taking its trading gains in cash, the company will instead take those profits in the form of Goldman shares. The new deal will give Berkshire a nearly 2% stake in the Wall Street mainstay, a business Buffett said he has been making deals with for more than 50 years.