China tested a nuclear-capable hypersonic missile in a move that caught U.S. intelligence by surprise, according to a new report.

The missile launched in August and circled the globe before speeding towards its target, which it missed by about two-dozen miles according to three individuals briefed on the intelligence. Two of those individuals said the test showed how far China has progressed on hypersonic weaponry – farther than U.S. officials realized.

“We have no idea how they did this,” one individual told The Financial Times.

Taylor Fravel, an expert on Chinese nuclear weapons and professor at MIT, said it would be “destabilizing” if China fully developed and deployed such a weapon.