How to stop adb shell from echoing every command?

On Windows 7 X64, adb shell (run from cmd.exe) repeats every command that I enter:

>adb shell
root@flame:/ # pwd
pwd
/

When I connect from Linux, this problem does not occur.

I tried with a Lenovo tablet running Android 4.2.2, and with a Flame running the latest Firefox OS nightly. Firefox OS is built on top of Android's HAL, which explains why it is possible to connect by adb.

adb version on both systems: 1.0.32