HSBC has banned customers of its online share-trading platform from buying or moving into their accounts MicroStrategy Inc stock, a message seen by Reuters showed, calling it a “virtual currency product”.

The bank will not facilitate the buying or exchange of products related to or referencing the performance of virtual currencies, the message to an HSBC InvestDirect client said. Bitcoin is the largest and best-known virtual currency.

MicroStrategy declined to comment. The U.S. business software firm is led by bitcoin proponent Michael Saylor and owns bitcoin worth billions of dollars.

While HSBC will allow the holding, sale and outgoing transfer of MicroStrategy shares, it will forbid new purchases or incoming transfers, said the message dated March 29.