The U.K.’s Financial Conduct Authority (FCA) is proposing crypto rules that could quietly expand the definition of custody, potentially sweeping in platforms and software providers that don’t consider themselves custodians.

The FCA published its Cryptoasset Perimeter Guidance on Wednesday, which includes a few technical traps for firms handling clients’ crypto assets.

The rules draw a red line at the 24-hour mark for custody. Any firm or crypto platform or app holding client assets for longer than a day during trade settlement will likely fall under the regulated custodian classification, which triggers a requirement for a full safeguarding-license.

Validators and node operators also need to proceed with caution. The regulator warned…