diff --git a/scripts/upgrade b/scripts/upgrade
index 74be857..8a7ecea 100644
--- a/scripts/upgrade
+++ b/scripts/upgrade
@@ -88,11 +88,11 @@ pushd $final_path
         sed -i "/HTTP_PORT/s/[0-9]*[0-9]/$port/" package.json
         sed -i "/HTTPS_PORT/s/[0-9]*[0-9]/$https_port/" package.json
 
-        TMP_HOME=$HOME
+	[[ -v HOME ]] && TMP_HOME=$HOME
         HOME=$(pwd)
         ynh_use_nodejs
         ynh_npm install
-        HOME=$TMP_HOME
+        [[ -v TMP_HOME ]] && HOME=$TMP_HOME || unset HOME
 popd
 
 #=================================================