Introduction of env --null

I have tried to extract environment variables in a Python process with help of env --null, which works even for environment variables containing newline character.

But on some machines I have received an error:

> env -0
env: invalid option -- '0'

> env --null
env: unrecognized option '--null'

> env --version
env (GNU coreutils) 6.12
Copyright (C) 2008 Free Software Foundation, Inc.

In which version was the argument introduced? Is there any alternative command to extract the environment?