The first African-American member of Twitter’s board of directors — Debra Lee is stepping down from her position after three years of services at the micro-blogging platform.

The exact reasons for Lee’s departure from Twitter remain undisclosed as of now.

However, after Twitter, Lee would now be part of the board of directors at US-based telecom major AT&T.

“I believe Twitter has a bright future, and I wish Jack (Dorsey) and the entire company continued success,” CNET quoted Lee as saying on Monday.

Twitter, like other tech companies, has been under criticism for not having enough diversity on its board of directors.

When Lee joined Twitter’s board in 2016, civil rights activists praised Twitter’s decision.

Prior to joining Twitter, Lee served as the Chairman and Chief Executive Officer (CEO) of BET — the parent company for Black Entertainment Television.