As the sixth season of Real Housewives of Atlanta continues, a sneak peek reveals that cast member Porsha Williams has a major history flub in Sunday's episode of the show.

In the clip, the ladies are well into their trip to Savannah, G.A. and they visit an underground railroad path. The facilitator reveals that during the years of slavery, many who were trying to escape would use that exact same path to catch air while on the underground railroad.

While most of the co-stars seemed amazed to be standing in a historic place, Williams commented and said, "There had to be an opening at the railroad at some point. Somebody's driving the train. It's not electric like we have now, right?"

The facilitator could not help but give an awkward laugh and smile.

That's when cast members Kandi Burruss and Phaedra Parks attempt to pull Williams aside.

Burruss told Williams, "It wasn't a train baby."

Williams responded and said, "I'm thinking it was like widespread."

Given that Williams never fails to remind viewers that her grandfather, Hosea Williams, was known as a notable civil rights icon, Porsha's latest err on Real Housewives of Atlanta has the potential to raise many eyebrows, including her co-star and frenemy Kenya Moore.

Moore said, "It's almost hurtful to me to watch her be so dumb."

While Burruss and Parks seemed to try their best to explain that an underground railroad is just a "euphanism" for the method slaves used to escape, Williams still didn't seem to catch on.

She said, "But I know that one particular person made it. They actually...How did they get down there?"

Cynthia Bailey commented and said her grandfather was "probably rolling around in his grave."

Check out the clip below.

Real Housewives of Atlanta airs every Sunday on Bravo at 8/7c.