Cryptocurrency investors who are preoccupied with the ever-changing value of their virtual fortunes—particularly after bitcoin’s 28% drop in January—may be forgetting to ensure that this wealth can be passed down to their children and grandchildren.

The secretive nature of cryptocurrency, not to mention its digital format, means virtual currency investors with large holdings have to record their account details— preferably on paper—or risk losing everything for their heirs should something unexpected happen, experts say.

“People need to document that they own it, where they bought it, and how  someone can get access to it,” says Kevin Ruth, head of wealth planning and personal trust at Fidelity Investments’ Private Wealth Management.

Wealth managers and estate planning attorneys have only recently begun to grapple with the issues thrown up by their wealthy clients who have started dabbling in bitcoin and competing cryptocurrencies. Unlike other investments, you can sign up to buy virtual currencies on an exchange today “and not even use your own personal information,” Ruth says.

This could change, of course, if regulators begin to require identification, as is beginning to happen in South Korea. But for now, your heirs may not know if you have a cryptocurrency account if you haven’t told them, or more importantly, written down where it is and the private digital key needed to access it.

“Even though it exists in this virtual world of 1s and 0s floating around, it is property,” says James Lamm, an estate planning attorney with Gray Plant Mooty in Minneapolis who specializes in digital assets.

Complicating matters, the exchanges that exist, like Coinbase and Bitstamp, do not ask account holders to name a beneficiary, which is common with any other asset management account, Ruth says. That means, even if you’ve divulged the account’s existence, unless its named in your will, the currency’s fate will be determined through probate court, an expensive, time-consuming process.

When it comes to bitcoin, “people just talk about the price,” Ruth says. “Nobody is talking about what happens when you die.”

To make sure your virtual currency isn’t stranded in the ether, consult an estate planning attorney to update your will, your revocable living trust (if you have one) as well as your power of attorney authorization, a document that directs a specific person to act on your behalf, Lamm says.

“Those documents should include your wishes about how to distribute or delete any valuable or significant digital property,” he says. These legal documents should also be revised to allow fiduciaries acting on your behalf to access your computers, storage devices, accounts and data, authority that will prove useful for heirs trying to simply gain access to your digital family photos or Facebook account, let alone your bitcoin.

Separate from legal documents, which can become public, Lamm also advises clients to list any “valuable and significant” digital property, again from bitcoin to sentimentally important assets like Facebook or photos, with details on where the property is located, how to access it (i.e. usernames and passwords) and what your wishes are. Then put this list, whether it’s on a USB drive or paper, in “cold storage,” a safe deposit box or home safe.

For bitcoin and other virtual currencies, this means including how to access your encrypted “private key.” If you hold bitcoin on an exchange, the exchange might provide the private key to a fiduciary, but having the key will simplify the process. If you hold the currency in a private account and haven’t shared how to access it, “it’s gone forever,” Lamm says.