Mario Gabelli, founder of Gamco Investors Inc., said he’s a buyer of shares in Rolls Royce Holdings Plc, the aircraft-engine maker whose stock slumped 20 percent this month after warning that earnings next year would take a hit.

Gabelli, speaking in an interview with Betty Liu on Bloomberg Television Friday, cited growth in commercial aviation.

Gamco owned 20.3 million shares in Rolls Royce as of Aug. 3, according to data compiled by Bloomberg. Shares last traded at about 552 pounds ($838).

Rolls Royce said last week that 2016 earnings would take a 650 million-pound ($990 million) hit from slowing sales of business-jet engines and a slump in revenue from maintaining regional aircraft.

ValueAct Capital Management, an activist hedge fund, increased its stake in Rolls-Royce Holdings Plc above 10 percent, Rolls Royce said.