The 33-year-old outspoken comedian was scheduled to perform at the Colosseum at Caesar's Palace Thursday, but E! Online reported Chappelle has canceled the date for unknown reasons.
Now Maher, who had already been scheduled to perform after Chappelle at the festival, will simply extend his set to fill in the open time.
The cancellation comes as Chappelle attempts to repair his public image, damaged after the comedian walked away from a $50 million deal to produce his Comedy Central namesake TV series.
While Chappelle will not appear at the five day comedy festival, the annual event will be welcoming back Comic Relief to its ranks after an eight year absence.