diff --git a/data/helpers.d/utils b/data/helpers.d/utils
index 4501dcf1b..75347cc7c 100644
--- a/data/helpers.d/utils
+++ b/data/helpers.d/utils
@@ -576,7 +576,7 @@ ynh_app_upstream_version () {
     # Declare an array to define the options of this helper.
     local legacy_args=m
     local -A args_array=( [m]=manifest= )
-    local manifest
+    local manifest=""
     # Manage arguments with getopts
     ynh_handle_getopts_args "$@"