Elon Musk took to Twitter on Wednesday to announce that Tesla would no longer accept payment in the form of Bitcoin, citing environmental concerns associated with the mining process.

“We are concerned about rapidly increasing use of fossil fuels for Bitcoin mining and transactions, especially coal, which has the worst emissions of any fuel,” Musk tweeted. “Cryptocurrency is a good idea on many levels and we believe it has a promising future, but this cannot come at great cost to the environment.”

Tesla hasn’t issued an official statement on the matter, nor have they answered questions regarding the number of Teslas that have already been purchased via Bitcoin and whether Musk was previously aware of the environmental costs of cryptocurrency.  While Musk’s decision has left many perplexed, Dallas Mavericks owner Mark Cuban doubled down on his franchise’s use of Bitcoin and other cryptocurrencies. Tweeting in response to Musk, Cuban wrote: “We at http://Mavs.com will continue to accept BTC/Eth/Doge because we know that replacing Gold as a store of value will help the environment consumption… shrinking big bank and coin usage will benefit society and the environment.”