diff --git a/install.sh b/install.sh
index 00438dd..3c5455c 100755
--- a/install.sh
+++ b/install.sh
@@ -16,8 +16,6 @@ function upgrade {
 
 function install {
   echo INSTALL
-  MIAOU_BASH_DIR=/opt/miaou-bash
-  export MIAOU_BASH_DIR
 
   local tempfile
   tempfile="/tmp/$(basename "$MAIN_TAR_GZ_URL")"
@@ -59,6 +57,11 @@ set -Eeuo pipefail
 assert_supported_distro
 sudo_root
 
+if [[ ! -v MIAOU_BASH_DIR ]]; then
+  MIAOU_BASH_DIR=/opt/miaou-bash
+  export MIAOU_BASH_DIR
+fi
+
 deployment_type_adjective="${1:-installed}" # self-upgrade provides 'upgrade'
 if once_installed; then upgrade; else install; fi
 if [[ $deployment_type_adjective == 'installed' ]]; then