Love it or loathe it, Michael Jackson's posthumous single 'This Is It,' which debuted online Monday at midnight, seems destined to be a smash. That news should make crooner Paul Anka happy, as he's set for an influx of cash now that Jackson's estate has acknowledged his co-writing credit and agreed to give him 50 percent of the song's publishing rights.

"They did the right thing," Anka told the AP after threatening legal action over the tune he wrote with Jackson in 1983. "I don't think that anybody tried to do the wrong thing -- it was an honest mistake."

Fans quickly pointed out that Jackson 's recording of 'This Is It' was in fact an early take of the song that was ultimately recorded as 'I Never Heard' by Sa-Fire in 1991. Columbia/Epic Records chairman Rob Stringer publicly acknowledged the error today in a New York Times interview.

After 'This Is It' debuted, Anka told the paper, "It's exactly the same song. They just changed the title." The singer says he and Jackson originally planned to duet on 'I Never Heard,' which was set for Anka's 1983 album 'Walk a Fine Line.' Anka told the Times that Jackson took off with the master tapes, but once Anka revealed he had original multitrack tapes and other evidence that he co-wrote the track, he landed credit for the song from Jackson's estate. The song is the centerpiece of the upcoming documentary, also titled 'This Is It,' which was filmed during Jackson's rehearsals for his London O2 Arena shows.