Things got a bit awkward during Tuesday night’s Democratic presidential primary debate when Sen. Bernie Sanders (I-VT) and Sen. Elizabeth Warren (D-MA) quibbled over whether the Massachusetts lawmaker was the only one on the stage to defeat a Republican incumbent in the past 30 years.

“Well, just to set the record straight, I defeated an incumbent Republican running for Congress,” Sanders declared, prompting Warren to softly ask: “When?” “1990,” the Vermont senator responded, causing Warren to count the years out. “That’s how I won. Beat a Republican congressman.”

The two went on to debate whether that win occurred in the “past 30 years” or “30 years ago,” with Warren insisting she was correct to say she was “the only one who’s beaten an incumbent Republican in 30 years.” Sanders, meanwhile, held his ground that 1990 was “30 years ago” and that’s when he beat a Republican to become a congressman.