Warren Buffett’s Berkshire Hathaway boosted its stake in Occidental Petroleum to 26.8% after getting the go-ahead last month from US regulators to buy as much as half of the oil giant.

The new level of ownership, reported late Friday in a federal filing, is up from 20.2% as of Aug. 8, according to data compiled by Bloomberg. 

Berkshire has spent this year expanding its ownership in Occidental after first making a bet on the Houston-based oil company three years ago. In approving Berkshire’s request on Aug. 19, the Federal Energy Regulatory Commission said the proposed stock purchases would be consistent with the public interest.