diff --git a/x230/prepare_before_installation.sh b/x230/prepare_before_installation.sh
index 5b398e9..91fa392 100755
--- a/x230/prepare_before_installation.sh
+++ b/x230/prepare_before_installation.sh
@@ -43,7 +43,7 @@ done
 hash dmidecode
 
 LAPTOP=$(dmidecode | grep -i x230 | sort -u)
-if [ -z $LAPTOP ] ; then
+if [ -z "$LAPTOP" ] ; then
 	echo "This is no Thinkpad X230. This script is useless then."
 	exit 0
 fi