Binance, the world’s largest crypto exchange, has temporarily suspended all spot trading, deposits and withdrawals citing an “issue” that it’s working to resolve.

“Initial analysis indicates matching engine encountered a bug on a trailing stop order (a weird one),” Binance founder and chief executive Changpeng Zhao said in a tweet, adding that the firm expects things to recover within two hours.

Binance commands over 60% of all crypto spot volume. It has also increased its market share of Bitcoin spot volume to over 90% in recent quarters, thanks to zero commissions, according to according to Arcane Research.

Bitcoin fell 1% to $27,649 and Ethereum fell 2% to $1,751 on the news before recovering slightly.