diff --git a/lib/self-upgrade.bash b/lib/self-upgrade.bash
index c4b785a..df90229 100755
--- a/lib/self-upgrade.bash
+++ b/lib/self-upgrade.bash
@@ -33,7 +33,7 @@ function bootstrap {
 # MAIN
 
 [[ "$UID" -ne 0 ]] && echo 'root privilege required' && exit 1
-
+[[ ! -v MIAOU_BASH_DIR ]] && export MIAOU_BASH_DIR="$DESTINATION/miaou-bash"
 current=$(miaou-bash --version)
 latest=$("$MIAOU_BASH_DIR/tools/wget_semver" artcode miaou/miaou-bash)