ABC had been promoting last night’s 20/20 as an “exclusive” that would have featured “never before seen” tapes from O.J. Simpson’s deposition in the 1997 civil suit over the deaths of Nicole Brown Simpson and Ron Goldman.

Turns out they were seen before: on NBC. The Peacock’s news program “Dateline” aired the tapes three times, in 1999, 2004 and 2014.

ABC News issued an apology for the mistake. “We were wrongly under the impression these deposition tapes were exclusive and had not aired before at length,” said a spokesperson in a statement. “We learned this morning portions did air 15 years ago. We apologize for the mistake.”

“Dateline” couldn’t resist pointing out the “exclusive” was anything but, with a tweet from the show’s account. “Oh, hey @abc2020 @GMA partying like it’s 1999! Check out #Dateline logo from first time we aired the tapes! #retro”

“20/20” tweeted back in response: “Dear @DatelineNBC You’re right, we were wrong, but it’s still a good show! Be sure to watch!”

Later promotions of the program referred to the tapes as “rarely seen” and “forgotten.”