Cryptocurrency exchange Poloniex has announced a new scheme to reimburse users affected by an unexpected “flash crash” that saw 1,800 BTC ($20 million) wiped from its margin trading lending pool in May.

An official blog post promises to return trading fees (in Bitcoin) to impacted lenders until all losses have been repaid.

“Every time you pay a trading fee, we will convert the fee to BTC and then credit you those fees each day. Your first credit will include all the trading fees you have paid since June 6, 2019,” wrote Poloniex.

Poloniex supports peer-to-peer margin trading, a system in which users send their Bitcoin BTC to a “lending pool” so that other users may borrow cryptocurrency to trade with larger stacks.

Lenders are supposed to receive interest for doing so, and borrowers must keep collateral to ensure that debts can actually be repaid.

Bitcoin margin trading and flash crashes do not mix

In late May, the value of an obscure token named Clams (which was available for margin trading through Poloniex) suddenly crashed by almost 80 percent in under 45 minutes.

Usually, this scenario should trigger the exchange to close the positions of borrowers – a move designed to protect the capital of cryptocurrency lenders by cutting borrower’s losses as soon as possible to ensure they can repay their debt.

As it turned out, the sheer velocity of the Clams market crash actually caused malfunctions in Poloniex’ automated liquidation system, leaving its lenders to be collectively out-of-pocket 1,800 BTC (worth roughly $13.5 million at the time).

So far, Poloniex has paid back just over 180 BTC ($2 million) to those users.

“Our work to make [affected] customers whole isn’t limited to our first payment or this new step of crediting trading fees. We are actively pursuing other strategies, and will update […] when we can,” said Poloniex. “We understand how upset customers are with this loss and we appreciate [their] patience. In addition to being committed to making [them] whole, we remain dedicated to earning back [their] trust.”

Other popular cryptocurrency exchanges have also had troubles with suddenly illiquid markets. Last December, the price of Ethereum briefly collapsed from $100 to a measly $13 on Coinbase Pro.