diff --git a/vpnupgrade_Libreswan_centos.sh b/vpnupgrade_Libreswan_centos.sh
index 3903f8d..081e012 100644
--- a/vpnupgrade_Libreswan_centos.sh
+++ b/vpnupgrade_Libreswan_centos.sh
@@ -18,7 +18,7 @@ if [ ! -f /etc/redhat-release ]; then
   exit 1
 fi
 
-if grep -qs -v -e "release 6" -e "release 7" /etc/redhat-release; then
+if ! grep -qs -e "release 6" -e "release 7" /etc/redhat-release; then
   echo "Sorry, this script only supports versions 6 and 7 of CentOS/RHEL."
   exit 1
 fi