Ed Sheeran’s being sued in America over claims that Thinking Out Loud rips off a Marvin Gaye song.
The family of the man who co-wrote Let’s Get It On says it copies key parts of the track.
Ed Townsend’s relatives are asking for a jury to decide if they’re owed damages.
“The Defendants copied the heart of Let’s and repeated it continuously throughout Thinking,” the court papers claim.
“The melodic, harmonic, and rhythmic compositions of Thinking are substantially and/or strikingly similar to the drum composition of Let’s,” it says.
There’s been no response yet from Ed Sheeran or his record label.
The lawyer representing the Marvin Gaye estate told Newsbeat they were “aware” of comparisons with the 1973 hit.
Ed’s already being sued for $20m (£13.8m) over his single Photograph, which two US musicians say copies their song Amazing.
The Gayes’ lawyer, Richard Busch, is also representing Halo Songs, who’ve launched that case.
Thinking Out Loud won best pop solo performance at this year’s Grammy awards and was a multi-platinum hit globally.
It was also Ed’s highest charting hit in North America, reached number one on the Official Singles Chart in the UK and became the first song to spend a full year in the UK’s top 40.
It was also the first ever song to hit 500 million streams on Spotify.
The song is currently credited to Ed Sheeran and Amy Wadge. It was released by Atlantic Records and published by Sony/ATV.
If Ed’s team, label and publishing companies don’t come to an amicable agreement with Ed Townsend’s estate, the case could go to court.
People have noticed the similarities of the two tracks in the past.