Republican presidential candidate Jeb Bush made light of his admission to smoking marijuana four decades ago amid Wednesday night's GOP debate.

"So 40 years ago I smoked marijuana, and I admit it," the former Florida governor said while smiling during the main-stage debate in California.

"I'm sure that other people might have done it and might not want to say it in front of 25 million people. My mom's not happy that I just did," Bush said.

His Twitter account followed up with an apology to the former first lady:

Sorry Mom — Jeb Bush (@JebBush) September 17, 2015

Bush acknowledged in a Boston Globe profile early this year that he smoked marijuana during his prep school years, saying, "It was pretty common."

The GOP candidate's remark on marijuana Wednesday came during a debate segment on regulation for the drug and other illegal substances.

"We have a serious epidemic of drugs that goes way beyond marijuana," Bush said, pointing to heroin overdoses in New Hampshire.

Paul argued Bush campaigned against medical marijuana in Florida, invoking the story of a young girl being unable to treat an illness with cannabis oil.

"And if they attempt to do that in Florida, they will take the child away, they will put the parents in jail, and that's what that means: If you're against allowing people to use medical marijuana you'll actually put them in jail," he said.

"Under the current circumstances, kids who have privilege, like you do, don't go to jail, but the poor kids in our inner cities go to jail," Paul said to Bush.

"I don't think that's fair," the senator added.

Bush pushed back, saying of medical marijuana, "As a citizen of Florida, I voted no."

Paul similarly pushed back on New Jersey Gov. Chris Christie, who maintained that he would enforce the federal law on states like Colorado that have legalized recreational marijuana.