diff --git a/setup/so-functions b/setup/so-functions
index 52865b5f1..8213cd516 100755
--- a/setup/so-functions
+++ b/setup/so-functions
@@ -331,7 +331,7 @@ collect_es_space_limit() {
 collect_fleet_custom_hostname_inputs() {
 	whiptail_fleet_custom_hostname
 
-	while ! valid_fqdn "$FLEETCUSTOMHOSTNAME" || [[ $FLEETCUSTOMHOSTNAME != "" ]]; do
+	while [[ -n $FLEETCUSTOMHOSTNAME ]] && ! valid_fqdn "$FLEETCUSTOMHOSTNAME"; do
 		whiptail_invalid_input
 		whiptail_fleet_custom_hostname "$FLEETCUSTOMHOSTNAME"
 	done