Microsoft, which has been floated as a potential purchaser of TikTok to ameliorate concerns over the app’s links to the Chinese Communist Party, created an operating system explicitly for the Chinese government in collaboration with a Chinese military proxy.

Adding to a long list of reasons why Microsoft acquiring TikTok would not remedy concerns over the app’s subservience to the Chinese Communist Party, the American tech giant built a version of its popular “Windows” operating system for use by the Chinese government in 2015.

According to the company’s press release:

“China Electronics Technology Group (CETC) and Microsoft Corp. announced a partnership aimed at providing world-class operating system technology and services for Chinese users in specialized fields in government institutions and critical infrastructure state-owned enterprises.”

The statement fails to mention, however, that state-owned CETC has been identified by the U.S. Department of Defense as collaborating with the People’s Liberation Army (PLA) since at least 1999.

CETC was also recently targetted by the Trump administration for its role building military islands in the South China Sea, with the Commerce Department adding the company to its “Entity List.” Originally created to stop American products from assisting weapons of mass destruction programs in 1997, the designation makes companies subject to stricter licensing requirements to do business in the U.S.

Labeled the “Windows 10 China Government Edition,” Windows Executive Vice President Terry Myerson detailed how the company has “earnestly cooperated with the Chinese government on the security review of Windows 10.

Equally concerning, Myerson outlines how governments across the world use a similar Windows operating system. In other words, Microsoft has given China, notorious for hacking, cyberattacks, and espionage, unfettered access to a platform comparable to one utilized by the U.S. government:

“Windows 10 is the most secure version of Windows ever, and we’re humbled that governments around the world like the U.S. Department of Defense, the Australian Health Department, and the Italian Ministry of Defense are choosing Windows 10 for their security, and now the Chinese government has a version of Windows created specifically for it.”

While CETC retains 51% of the venture while Microsoft retains the remaining 49%, little is known about the changes Microsoft and Windows effectuated on the operating system.

The collaboration is just one example of the company’s extensive relationship with the Chinese Communist Party – a concerning prospect given the company’s business interests and market access could be used a point of leverage should Microsoft acquire TikTok.