An American man has served a 13-year prison sentence, even though officials forgot to lock him up.

After his sentencing for armed robbery of a Burger King manager in 1999, Cornelius Anderson was never contacted by Missouri's corrections department.

The error was only realised when he was due for release.

Over 35,000 people have signed a petition on Change.org to help him avoid serving out his sentence.

In the meantime, he has stayed out of trouble, started a family and a business, and he's relieved he won't now be locked up:A man claiming to be Mike's brother on Change.org has said;

"Mike is my brother and I love him to death. That being said, that's not the only reason I'm signing this petition. I'm signing the petition because my brother became the man prison purports to rehabilitate inmates into. He wasn't being a law abiding citizen out of fear or to avoid getting caught, he was a law abiding citizen because that's who my brother is. He's a good man who understands that as a young man, he made mistakes but as a father and husband, he has far too much to lose now. Please, let my brother get back to being a contributing, productive member of society. His children need him, his wife needs him and, selfishly, his siblings and family need him as well."