DMX has reportedly backed out of his upcoming December celebrity boxing match, when the promotion company refused to fix the fight so he'd win.

Thunder Promotions has found a replacement to step in ... another rapper by the name of Coolio.

According to TMZ, Coolio has signed on to replace X for the upcoming December 12th match in Alabama, and has been much easier to deal with.

"He is going to take this seriously," the company told TMZ.

DMX had previously agreed to fight actor Eric Martinez, but is now out of the mix, says reports.

Thunder Promotions is said to be preparing a lawsuit against X for breach of contract.