Berkshire Hathaway nearly doubled its stake in U.S. homebuilder Lennar to approximately 10.9%. September share purchases brought Berkshire’s total investment to about $2.1 billion.

Regulatory filings disclosed the increased stake after Berkshire’s ownership crossed 10%, a threshold that requires more immediate disclosure. The purchases were likely directed by one of Berkshire’s portfolio managers.

The investment comes amid a challenging housing market and a slump in builder valuations. It points to a bullish long-term outlook on homebuilding stocks despite recent headwinds. The market reacted positively to the news.