Travelers leaving San Diego Comic-Con on United Airlines got an unwelcome surprise this weekend, when United said that comic books were banned in checked luggage. United claimed this was a TSA-mandated rule for all airlines operating out of San Diego — only to have the TSA publicly refute United’s claim on Twitter.

As The Consumerist reported yesterday, United posted a notice telling “Comic-Con attendees [to] remove all books from checked bags.” When people complained on Twitter, United confirmed the news. “The restriction on checking comic books applies to all airlines operating out of San Diego this weekend and is set by the TSA,” a spokesperson wrote. From there, things got even weirder: it told one confused attendee that only comic books were banned in checked baggage, while regular books were “A-OK.” But then, the TSA categorically denied this rule’s existence, saying that all books were fine in both checked and carry-on baggage.

If you are at #SDCC #SDCC2017 and are flying out on @united - please take note of this and share!!! pic.twitter.com/s1sV269DuQ — Adi Chappo (@adichappo) July 23, 2017

“They are incorrect. There is no problem with [people] taking comic books, which are not a security threat, in their checked baggage,” TSA spokesperson Lorie Dankers told The Verge. “The bottom line is, there's no restriction. We're working with United Airlines to figure out where this is coming from.” The agency also posted a tweet telling United that there was no rule about checking books of any kind.

A TSA spokesperson told The Consumerist that it would contact any airlines that promoted this “rule,” but as far as we know, only United posted anything about it. Dankers described a previous incident where Southwest Airlines incorrectly advised against packing glossy magazines, but said it was unrelated. It’s not clear how widely United enforced its fake restriction, although the aforementioned attendee apparently did end up packing her comics in a carry-on.

Good afternoon. Pls note there are no TSA restrictions on checking comic books or any other types of books. https://t.co/Nu00IvcZSc — TSA (@TSA) July 24, 2017

So how did this happen? Dankers didn’t speculate, but it’s possible that United massively misread a 2016 TSA blog post aimed at Comic-Con attendees. In a list of “suggestions” for packing, it advised putting brochures, comic books, and magazines in carry-on bags instead of checked luggage, because large stacks of them could trigger bag searches that slowed down security. But that was a logistical guideline, not a literal security rule.

A statement from United backs that interpretation up. “While TSA is recommending that customers keep their comic books in their carry-on bags, there are no restrictions on packing them in checked luggage,” said a spokesperson. “We misunderstood TSA’s instructions and regret any inconvenience this may have caused our customers.”

This isn’t the first book-related TSA scare we’ve had this year. In May, a report suggested that people might have to start taking all books out of carry-on bags during security screenings, something the agency later said was part of a small, discontinued test program. It’s not often you see the TSA come out of an airport security story looking like the heroes.... but then again, it’s hard to find an airline that’s more widely hated than United, too.

Update 5:15PM ET: Added statement from United.