Bill Clinton said his wife has suffered fainting spells in the past, raising the specter that Hillary Clinton’s health might be worse than he — or her doctors — realize.

The former president made the disclosures in an interview with CBS’s Charlie Rose, after the host commented, “[W]hen you look at that collapse, that video that was taken, you wonder if it’s not more serious than dehydration.”

Rose was referring to Hillary Clinton’s early exit from a 9/11 memorial. Video showed the Democratic presidential nominee collapsing as she entered a Secret Service vehicle. Her presidential campaign later revealed she had been diagnosed with pneumonia.

“Well, if it is, then it’s a mystery to me and all of her doctors,” Bill Clinton said.

The candidate’s spouse then said his wife “frequently” suffers medical episodes like the one she had Sunday — before quickly correcting himself to say she “rarely” has such episodes.

“Because frequently — well, not frequently, rarely — but on more than one occasion, over the last many, many years, the same sort of thing happened to her when she got severely dehydrated,” said the former president.

Clinton said his wife’s most recent episode came after working hard before the fall. “[S]he had two-and-a-half hard days before the day when she got dizzy,” he said.

Hillary Clinton is taking several days off the campaign trail to recover from her illness. Bill Clinton is stepping in for his wife, attending fundraisers and a rally in her place.