Twitter has removed a series of fake campaign ads trying to convince Clinton voters that it’s possible to vote by text.

The fake ads were spotted yesterday by Robert McNees, a physicist at Loyola University Chicago, who reported them to Twitter only to receive word back that the tweets didn’t violate the site’s terms of service, despite spreading false information and attempting to disenfranchise voters.

BuzzFeed News later picked up the story, bringing it to Twitter’s attention. Twitter CEO Jack Dorsey responded about an hour later, saying, “Not sure how this slipped past us, but now it's fixed.”

Twitter just informed me that attempting to disenfranchise voters is not a violation of their Terms of Service. @jack @Support pic.twitter.com/YXVdt8sHwA — Robert McNees (@mcnees) November 2, 2016

At least one account tweeting the fake ads has been banned — but it happened to be the account of a self-proclaimed “hero of the racist alt-right movement” who had already had an earlier account suspended. Another account, with over 17,000 followers, that tweeted a fake ad just had their tweet removed.

The images went around enough that the Clinton campaign seems to have caught onto them. As BuzzFeed noticed, either the Clinton campaign or the group the happened to be operating the advertised number, iVisionMobile, has taken control of it. Anyone texting “Hillary” to 59925 now receives a clarification that “the ad you saw was not approved” and an offer to subscribe to the actual Clinton text-message list.

While it’s not clear how widespread the ads were, they evidently had enough reach to get a correction straight from the advertised number. And at this point, a search on Twitter brings up more stories debunking these images than people asking about voting by text.

Still, the incident speaks to Twitter’s continued trouble with reviewing reported tweets — and its tendency to let things slide. Having to govern speech across an entire website is no easy task, but there continue to be obviously problematic tweets that make it through review.