The funnyman agreed to pen the foreword to a book called Make 'Em Laugh, about the history of New York City comedy club Comic Strip where Rock began his stand-up career.
However, the publishers moved the deadline and asked Rock to hand over his work early, according to New York Post gossip column Page Six.
Rock was at Cannes to promote his new animated film Madagascar 3: Europe's Most Wanted when he got the news, and had to spend all his free time working on the piece.
A source tells the publication, ""He got word that the publisher moved up the production schedule and needed his introduction right away. Chris was kind enough to write it while he was in Cannes, and sent it right over to make the deadline.""
The book by Richie Tienken and Jeffrey Gurian is due for release on 1 October (12).