Antpool, a cryptocurrency mining pool that manages a network of Bitcoin miners, has offered a refund to the user who sent the highest-ever fee for a transaction last week.

In an announcement on Thursday, Antpool said it would refund the 83 BTC to the user, saying that its risk control system had temporarily frozen the amount when packaging the transaction.

The team behind the mining pool asked the user to verify his or her personal identity either by preparing Electrum or Bitcoin Core signing tool, rousing the private keys of the address associated with the transaction to sign the message “AntPool.” The user will have until Dec. 10 to prove their identity.

On Nov. 23, a Bitcoin wallet address attempted to transfer 139.42 BTC to another address, but ended up spending 83.7 BTC on transaction fees, which was captured by Antpool on block 818087.

The whopping transaction fee was worth around $3 million at the time and is the highest amount spent on gas fees

Pseudonymous mempool developer “mononaut” commented that the user in question likely wasn’t aware of the replace-by-fee (RBF) node policy which allows an unconfirmed transaction in a mempool to be replaced with another one to get it cleared faster.

This isn’t the first time a blockchain user has sent an outlandish transaction fee because of a mixup. Earlier this year, stablecoin issuer Paxos sent a Bitcoin transaction with a fee of $500,000 to move just $2,000 worth of BTC.