I argued last month that given a price-to-free-cash-flow ratio of 10, “dividend payments at about 4.3% annually,” and plans “to buy back $1.2 billion in stock … the case for buying Sirius XM Holdings (SIRI 8.70%) stock is only getting stronger.”

Turns out, someone was listening.

Shares of Sirius stock gained 8.1% through 10:45 a.m. ET Monday after Warren Buffett investment vehicle Berkshire Hathaway (BRK.A 0.15%) (BRK.B 0.26%) revealed in an SEC filing that it has increased its stake in the satellite radio company.

What’s Buffett bought now?

Specifically, Berkshire Hathaway advised the SEC that from Oct. 9 to Oct. 11, it purchased 3.6 million Sirius shares. Added to its existing holdings, this gives Berkshire a stake of 108.7 million shares in the company, 32% of all shares outstanding.

(To be even more specific, S&P Global Market Intelligence data show that Berkshire owns about 6.6% of Sirius shares directly, while a further 25.5% are owned by New England Asset Management, which is a subsidiary of General Re Corporation, which is in turn a subsidiary of Berkshire Hathaway.)

Should you buy Sirius stock, too?

Clearly, Warren Buffett sees something he likes in Sirius stock, but should you like Sirius stock, too?

Sirius shares have gained nearly 20% since I first highlighted the stock as a potential bargain one month ago. But there’s still value there. Sirius sells for a P/E ratio of only 7, but most analysts who follow the stock see earnings growing at 12% annually over the next five years.

Granted, Sirius does carry a lot of debt — enough to make its enterprise value about twice its apparent market — and this can’t be ignored. However, free cash flow exceeds reported net income, too, resulting in an enterprise-value-to-free-cash-flow ratio of 15.

On 12% projected growth, and with a dividend still yielding a fat 4.3%, Sirius remains cheap enough to buy.