Bitcoin hit a two-week peak just shy of $40,000 on Monday, after another weekend reacting to tweets from Tesla boss Elon Musk, who fended off criticism over his market influence and said Tesla sold bitcoin but may resume transactions using it.

Axar.az reports citing foreign media that Bitcoin has gyrated to Musk’s views for months since Tesla announced a $1.5 billion bitcoin purchase in February and said it would take the cryptocurrency in payment. He later said the electric car maker would not accept bitcoin due to concerns over how mining the currency requires high energy use and contributes to climate change.

“When there’s confirmation of reasonable (~50%) clean energy usage by miners with the positive future trend, Tesla will resume allowing Bitcoin transactions,” Musk said on Twitter on Sunday.