diff --git a/lib/self-upgrade.bash b/lib/self-upgrade.bash
index 4485263..6f6f6ff 100755
--- a/lib/self-upgrade.bash
+++ b/lib/self-upgrade.bash
@@ -13,7 +13,9 @@ latest=$("$MIAOU_BASH_DIR/tools/wget_semver" artcode miaou/miaou-bash)
 
 if [[ "$current" == "$latest" ]]; then
   echo "up-to-date version: $current"
-  MIAOU_BASH_DIR='' source ../install.sh
+  export -n MIAOU_BASH_DIR
+  unset MIAOU_BASH_DIR
+  source ../install.sh
 else
   MIAOU_BASH_DIR='' source ../install.sh
 fi