Carl Icahn, the billionaire activist investor urging Apple Inc. to buy back $150 billion of its shares, at the end of September owned a stake of 3.88 million shares in the iPhone maker worth $2.05 billion, a filing showed Thursday.

The holding, as of Sept. 30, is part of Icahn’s drive to get Apple to deploy more of its cash to return value to shareholders. He sent a letter to Chief Executive Officer Tim Cook last month urging the company’s board to increase stock repurchases.

The investor said in the letter that he increased his holdings in Apple to 4.7 million shares, a figure that wasn’t reflected in Thursday’s filing with the U.S. Securities and Exchange Commission since it tallied numbers only through the end of September. Icahn has indicated that he intends to buy more of the stock that he said is undervalued.

Icahn is lobbying for a heftier payout just months after Cupertino, California-based Apple announced a plan for a total of $100 billion in dividends and buybacks.