As investors scramble to get their hands on shares of AI companies of all stripes, Anthropic this week updated its website to warn investors that a slew of private and secondary investment platforms that offer access to shares in the AI company are not, in fact, allowed to do so.

The company named Open Doors Partners, Unicorns Exchange, Pachamama Capital, Lionheart Ventures, Hiive (new offerings), Forge Global (new offerings), Sydecar, and Upmarket as companies that are not authorized to provide access to buy or sell its shares.

“Any sale or transfer of Anthropic stock, or any interest in Anthropic stock, offered by these firms is void and will not be recognized on our books and records,” the company’s support page reads.

Reached for comment, Forge Global claimed to have been included erroneously. “We are working with Anthropic to remove Forge’s name from this alert,” the platform told TechCrunch. “Forge does not facilitate transactions in any private company’s shares without the explicit approval of the company.”

Sydecar, meanwhile, said it only acts in an administrative capacity. “The company does not buy or sell securities or solicit transactions in any private companies. Further, Sydecar requires sponsors to attest that they have reviewed relevant documents relating to the transferability of shares and that they have the required approvals and consents from the company,” the company said in an emailed statement.

Anthropic’s update comes alongside a rise in the number of investment platforms offering exposure to AI companies’ shares (and thus their growth) via secondary markets where existing shareholders sell their shares, “tokenized” securities, special purpose vehicles (SPVs), or secondary market holdings.

The company, rumored to be raising fresh funding at a $900 billion valuation, has especially been in demand, with some secondary market brokers telling TechCrunch last month that it’s one of the “hardest” stocks to source.

“Anthropic is right to take seriously concerns around unauthorized share sales and investment scams,” Hiive spokesperson Dakota Betts said in an emailed statement. “We share those concerns. They are a major reason why Hiive invested heavily in legal, compliance, and diligence infrastructure from the beginning, and all share transfers facilitated by Hiive are approved by the issuer.”

Over the past year, some crypto companies, like crypto exchange OKX, have spun up investment products selling exposure to AI companies. These often take the form of pre-IPO perpetual futures contracts, which are derivative instruments that track the value of private companies on secondary markets but don’t offer ownership of actual shares.

SPVs are different from those derivative systems, offering investors a chance to buy shares of an entity that holds at least some stake in Anthropic. That equity could be from an official investor or could have been acquired when an investor is forced to liquidate its holdings, as happened during the bankruptcy of FTX. In other cases, the equity claim may be entirely fraudulent.

Anthropic says both its preferred and common stock are subject to transfer restrictions, which means any share sale or transfer not approved by its board of directors will be considered invalid. According to Anthropic, any third-party platform (specifically SPVs and retail investment firms) that claims to sell its shares directly or using forward contracts are unauthorized to do so.

“We do not permit special purpose vehicles (SPVs) to acquire Anthropic stock and any transfer of shares to an SPV are void under our transfer restrictions,” the company’s blog reads. “Offers to invest in Anthropic’s past or future financing rounds through an SPV are prohibited.”

Note: This story was updated to include comments from Hiive and Sydecar.