SmileDirectClub, a Warby Parker-style company that sells 3D-printed teeth aligners online that are typically cheaper than braces, has asked some customers dissatisfied with the product to sign extremely restrictive nondisclosure agreements that stifle them from saying anything negative about the company in order to get a refund, according to a report from The New York Times published on Wednesday.

An excerpt of a SmileDirectClub NDA included in the NYT’s story said that the person signing “will not make, publish, or communicate any statements or opinions that would disparage, create a negative impression of, or in any way be harmful to the business or business reputation of SDC or its affiliates or their respective employees, officers, directors, products, or services.”

In an email to The Verge, a SmileDirectClub spokesperson says those parts of the agreement are “negotiable,” which is a good thing to know if you’re attempting to get a refund yourself. (If you find yourself unable to negotiate them away, please let us know.)

For its story, The New York Times spoke to seven people who said SmileDirectClub’s teeth aligners didn’t work, and four said they had to get additional dental work to correct problems created by the aligners. I also thought it was wild that SmileDirectClub has apparently had over 1,670 Better Business Bureau complaints since 2014.

SmileDirectClub’s aggressive tactics to shut down negative online conversation about its products also bring to mind tactics used by online mattress company Casper, as chronicled by Fast Company in 2017 (another story you should read, by the way).

Casper sued three mattress bloggers who recommended other mattresses over Casper, alleging false advertising and deceptive practices. (Casper claimed the mattress bloggers were not properly disclosing financial relationships with companies whose products they were promoting over Casper’s.) Eventually, all three sites settled with Casper, though two of them took down their negative reviews and one was bought by a company that had financial support from Casper shortly before the settlement was finalized.

Update, January 24th at 10:11 PM ET: Added detail from a SmileDirectClub spokesperson, and removed a comparison to the Better Business Bureau reviews for Align, which doesn’t quite seem fair given that more people are likely to complain about a direct-to-consumer service like SmileDirectClub than they are about a product only offered through their dentist — as opposed to complaining about their dentist directly.