When writing bash shellscripts, I always set options "set -ueC" for strict error checking. However, loading pyvenv's activate and deactivate scripts from bash with "-u" option, they are failure because they may refer undefined shell variables. I hope activate script and deactivate function are enclosed like following block _OLD_BASH_OPTIONS="$-" set +u ### script body ## set -$_OLD_BASH_OPTIONS unset _OLD_BASH_OPTIONS Another option, all shell-variables in the script change like $SPAM -> ${SPAM:-}