Microsoft employees are circulating a letter supporting an effort to get its GitHub subsidiary to cancel a contract with the U.S. Immigration and Customs Enforcement agency, the latest effort among tech-company staff to influence corporate policy on government work.
The letter reflects concerns that Microsoft’s sales to the agency implicate the software maker in the government’s detention of immigrants. On Wednesday, GitHub employees protested the renewal of a roughly $200,000 contract with ICE after GitHub Chief Executive Officer Nat Friedman released an email defending the decision.
“As the parent company to Github, this contract with the U.S. Immigration and Customs Enforcement (ICE) makes all of us working at Microsoft complicit to the unethical detainment of tens of thousands of immigrants and the various abuses that ICE subjects them to,” read the letter, which was viewed by Bloomberg News. “Through our technology, we’ve already been contributing to the terrorism of ICE agents on our country’s immigrant population. We’ve been doing so for years.” It then calls on GitHub and Microsoft to cancel the contract.
The employees behind the letter asked to remain anonymous citing a fear of retaliation. Microsoft had no immediate comment.
The letter marks another sign of tension between rank-and-file tech workers and software giants, including Microsoft rivals Amazon and Google, which are increasingly aiming for lucrative government contracts. Microsoft employees also circulated an earlier petition asking the company not to bid on a massive Pentagon cloud-computing contract, called JEDI, and against efforts to sell its HoloLens augmented reality goggles to the U.S. Army. Microsoft executives have said that the company will continue to supply tech to the U.S. military.
The recent episode, however, is the first to involve GitHub, which makes a popular open-source software and has prided itself on a corporate culture that deifies programmers. The unit has its own management team and is run with some degree of independence from Microsoft.
In his email, Friedman said that ICE was using software management tool GitHub Enterprise Server and not the company’s more hands-on consulting services. “We do not know the specific projects that the on-premises GitHub Enterprise Server license is being used with, but recognize it could be used in projects that support policies we both agree and disagree with,” he wrote in a note published Wednesday. Friedman also pledged the company will donate $500,000 to nonprofits that help immigrant groups hurt by the policies.
Microsoft has been outspoken in its opposition to some of President Donald Trump’s immigration policies, including a travel ban that affects mostly muslim-majority countries. The company is a named plaintiff in the case opposing the termination of the federal Deferred Action for Childhood Arrivals program, which the Supreme Court will hear this term. Microsoft President Brad Smith received applause this week at a Seattle conference when discussing that stance.
At the same time, the company is a large supplier of software to the U.S. government and is in contention not just for JEDI but for a second massive military contract called DEOS, which will provide email, calendar, and collaboration tools. Earlier this week, Chief Executive Officer Satya Nadella spoke at the company’s Government Leaders Summit in Washington to tout work with the Interior Department and USDA.
More must-read stories from Fortune:
—Why WeWork’s failed IPO might not mean disaster for SoftBank after all
—Dyson pulls the plug on its plan to build an electric car
—Why Etsy sets a higher standard for diversity and inclusion in tech
—From porn to scams, deepfakes are unnerving business leaders and lawmakers
—A.I. remains a disruptive force in finance—even for fintechs
Catch up with Data Sheet, Fortune’s daily digest on the business of tech.