The family of the late-great rock star Prince Rogers Nelson has filed a lawsuit against his former doctor for failing to treat the singer’s opiate addiction, which ultimately led to his death.

As noted by The AP, Prince died of an accidental overdose of fentanyl April 21, 2016. The lawsuit alleges that Dr. Michael Schulenberg and others had “an opportunity and duty during the weeks before Prince’s death to diagnose and treat Prince’s opioid addiction and to prevent his death. They failed to do so.”

As previously reported, Prince lost consciousness on a flight home from a gig in Atlanta about a week before he untimely death. The plane made an emergency stop in Illinois, where he was said to have been revived at Trinity Medical Center in Moline with a drug that reverses opioid overdoses.

According to authorities, Schulenberg admitted to prescribing a different opioid to the artist in the days before he died, including oxycodone, which was issued under his bodyguard’s name to protect the Prince’s privacy. While Schulenberg has disputed that, he reportedly paid $30,000 to settle a federal civil violation alleging that the drug was prescribed illegally, NBC News reports.

READ MORE: Spike Lee nabs unreleased Prince song for the new movie, ‘BlacKkKlansman’

READ MORE: Aretha Franklin reportedly left an $80 million estate and no will

The family believes Schulenberg bears responsibility for Prince’s death and in their suit, they also name North Memorial Health Care, where the doctor worked at the time; UnityPoint Health, which operates the Moline hospital; and Walgreens Co., which operates two drug stores where Prince got prescriptions filled.

They are seeking unspecified damages in excess of $50,000.

Schulenberg’s attorney, Paul Peterson, said that they believe the lawsuit has no merit.

“We understand this situation has been difficult on everyone close to Mr. Nelson and his fans across the globe,” he said in a statement. “Be that as it may, Dr. Schulenberg stands behind the care that Mr. Nelson received. We intend to defend this case.”