In all the hoopla over AT&T’s deal to buy T-Mobile USA for $39 billion, it took a couple of days to recognize one of the collateral beneficiaries: Blackstone. But Bloomberg picked up the angle.

Blackstone bought a 4.4% stake in Deutsche Telekom, T-Mobile’s parent, in 2006 — one of the weirder deals the firm had done. Blackstone borrowed most of the money for the original investment, and DT dividends covered much of the interest cost, making it essentially a free call option on DT stock. The stock had been limping along at the time, so it seemed like there was more upside than downside, and with dividends covering the loans, it had a certain kind of logic, though some of Blackstone’s investors reportedly weren’t happy at the investment. After all, they don’t pay private equity managers a 1.5%-of-assets annual fee plus 20% of the profits to invest in public stocks that the investors could buy themselves without any middlemen.

Defying expectations, DT’s stock has been a dog since 2006, but it did get a lift when the AT&T deal was announced, bringing Blackstone a little closer to breakeven.