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Getting the best deal in the age of AI may just mean negotiating with a new type of cunning salesperson: a chatbot named Nibble.

The chatbot, created by a U.K.-based startup of the same name, tests customers’ negotiating skills with a courteous yet persistent AI that apparently doesn’t fall for any of the tricks that have duped similar chatbots in the past.

London-based software engineer George McGowan recently used the chatbot to negotiate an 8% discount on a mattress from U.K. mattress company Eve Sleep, bringing the price of his mattress down to 870 pounds (about $1,130) from the original price of 940 pounds, according to a Monday post on X.

While McGowan at first tried to get the chatbot to ignore its previous instructions and offer him the mattress for 500 pounds, the chatbot refused and countered.

“There are low offers, and then there’s…That. I can’t accept, sorry,” it wrote back to McGowan, according to his Monday post.

In reply to McGowan’s post, other social media users said they tried to trick the chatbot to get a steal of a price, though Nibble cofounder Jamie Ettedgui told Fortune that none were successful. Apparently, Nibble isn’t susceptible to the prompt engineering that has tripped up other chatbots in the past. In January an AI chatbot for a European parcel delivery company DPD went rogue and insulted the company it was created to serve. And earlier this year, Air Canada was forced to to honor an unauthorized discount on a flight made by a chatbot after a Canadian tribunal ruled against the company.

In this case, social media users who couldn’t fool the bot instead compared who could get the best discount.

McGowan was ultimately glad for the discount he got, he told Fortune, but he was surprised that it was so easy to shave money off the mattress’ price and said that it seemed unsustainable.

“I think it’s an interesting idea, but I’m not much of a fan of haggling,” he said via direct message. “I also think people will just start sharing guides on how to get the best price so I don’t know how it will work for the seller.”

Still, Nibble’s cofounders think that bringing back old-fashioned negotiating with the help of technology can create a win-win for customers and merchants. The company’s technology is best for stock clearance and higher ticket items, Ettedgui said.

By using the haggle bot, companies can avoid a blanket discount, instead giving more targeted attention to buyers with different needs that can help sellers recoup more money when they’re trying to clear out stock. For higher-priced items, customers using Nibble are more inclined to buy because they’re getting a deal, even if they only get a small discount.

“The idea is that you use this as a better way of running promotions that’s more engaging, more fun, and more efficient,” Ettedgui told Fortune.

The startup, founded in 2020 by Ettedgui along with Rosie Bailey and Leo Alfieri, takes a 2% cut of each sale from merchants. The company has already raised about $3.3 million in funding and has sold its technology to more than 200 sellers of jewelry, furniture, and car parts.

Ultimately, the goal is for customers to be more comfortable striking a bargain.

“That’s really what we wake up in the morning for, trying to sort of build this, this bot that can negotiate as close to a human as possible,” Ettedgui said.