Update to global variable aren't applied to jobs when envinject plugin is installed

how to reproduce :
running fresh 1.494, with a single Job to echo $FOO
FOO global variable set to "foo"

build #1 :
echo foo

change FOO to set value = "bar"

build #2 :
echo bar

Right, then install envinject (1.78), restart

build #3 :
echo bar

change FOO to set value = "qix"

build #2 :
echo bar

wtf ?