Apple CEO Tim Cook on Friday called on the U.S. House to approve the Employment Non-Discrimination Act (ENDA), which seeks to prohibit workplace discrimination based on sexual orientation and gender identity.

In a series of tweets, Cook reflected on the upcoming 50th anniversary of the Civil Rights Act of 1964.

In the first tweet, Cook embedded a black and white photo of Lyndon B. Johnson signing the legislation.

“'We shall overcome,'” Cook messaged to his more than 450,000 followers. “Reflecting on the 50th anniversary of the Civil Rights Act. Much done but much left to do.”

“The House should mark the 50th anniversary of the Civil Rights Act by passing ENDA,” he added.

Cook also recently called on Congress to approve ENDA while accepting a Lifetime Achievement Award from Auburn University, where the earned his bachelor's degree in industrial engineering.

(Related: Mike Coffman: Seventh House Republican to co-sponsor gay protections bill ENDA.)