Twitter CEO Jack Dorsey is preparing to step down, according to reports, raising questions about the social media platform’s future.

Dorsey currently serves as CEO of Twitter and his second company, Square. He has faced calls to step down from the top spot at Twitter before, with some questioning whether he has the ability to effectively run both companies.

According to CNBC, sources say Dorsey is expected to step down, although no details have been disclosed. It’s not known when or why he would step down, nor is it known who would replace him.

Twitter’s stock was up on the news.