Fastboot freezes on Mac OS Sierra I just got a new MacBook 2016 with Mac OS Sierra installed, after setting up my complete development environment and all required tools via Android Studio, I tried to flash a new Android Wear release on my watch. 

ADB is working without issues, but as soon as I try to run any fastboot command (other than fastboot help) it will completely freeze and never finish. 

It is just stuck with no output at all. 

I already tried to run it with sudo or reinstall it via the SDK Manager, I also tried different standalone fastboot binaries provided on XDA developers. 

There is nothing which seems to make it finish. Even "ctrl + c" won't exit the running command. Only killing it via the process list will work.
So this was an official Android fastboot bug. They are currently testing a fix in their QA department. 

With the new platform tools release it will be fixed:
https://code.google.com/p/android/issues/detail?id=231129