diff --git a/xCAT-genesis-scripts/usr/bin/dodiscovery b/xCAT-genesis-scripts/usr/bin/dodiscovery
index c23f99fae..aa90efc88 100755
--- a/xCAT-genesis-scripts/usr/bin/dodiscovery
+++ b/xCAT-genesis-scripts/usr/bin/dodiscovery
@@ -154,7 +154,7 @@ if [ "$flag_mtm" ] && [ "$MTM" != "unknown" ]; then
 	echo "<mtm>$MTM</mtm>" >> /tmp/discopacket
 fi
 flag_serial=`echo "$SERIAL" | sed 's/0//g'`
-if [ $flag_serial ] && [ "$SERIAL" != "unknown" ]; then
+if [ "$flag_serial" ] && [ "$SERIAL" != "unknown" ]; then
 	SERIAL=`echo $SERIAL | sed 's/\.//g'`
 	echo "<serial>$SERIAL</serial>" >> /tmp/discopacket
 fi