T-Mobile USA on Monday announced it would back Referendum 74, the Washington state ballot measure which if approved would uphold a gay marriage law enacted by lawmakers.

According to the Bellevue Patch, T-Mobile will donate $25,000 to Washington United for Marriage, the campaign to approve Referendum 74 in November.

“T-Mobile has a long-standing focus on creating an inclusive workplace environment for our employees,” Jim Alling, interim CEO of T-Mobile, said in a statement. “Our support of this issue is a reflection of our culture, how we do business, and our belief in the fair and equitable treatment of all employees.”

Zach Silk, campaign manager for Washington United for Marriage, welcomed T-Mobile's endorsement.

“We are very excited that T-Mobile has decided to take this important step in endorsing our effort to approve Referendum 74,” Silk said in a statement. “As one of the top employers in the Puget Sound area, T-Mobile's support demonstrates a commitment to employees, customers and communities in Washington state.”

The Bellevue-based cellular provider said more than 4,800 employees live and work in Washington.

Other Washington-based companies supporting marriage equality include Starbucks, Microsoft and Amazon. Last month, Amazon CEO Jeff Bezos and his wife MacKenzie gave $2.5 million to the effort.

(Related: Microsoft's Bill Gates, Steve Ballmer support Washington gay marriage.)