Coincidentally, Lil Nas X told PopBuzz back in July that he thought Billie was "great" and "amazing", hinting that he'd be interested in working with her in the future.
"Congratulations to billie eilish! u deserve this!" tweeted the 19-year-old rapper yesterday.
Old Town Road hasn't disappeared from the public conscience, though.
Like Lil Nas X, Eilish soared to fame over the past few months after releasing an acclaimed debut album When We All Fall Asleep, Where Do We Go? in March.
Lil Nas X isn't salty by any means. Eilish, 17, also become the first artist born after 2000 to top the chart.
That's longer than the 2017 hit Despacito, and pop juggernauts Mariah Carey and Boyz II Men's song One Sweet Day.
Billie Eilish is the new queen of the Hot 100.
Bad Guy set a record of its own.
One of Lil Nas X's many "Old Town Road" remix collaborators, Billy Ray Cyrus, also penned a congratulatory note to Eilish on Twitter and thanked supporters for "a hell of a ride".