diff --git a/update.sh b/update.sh
index 51a7984..e25682d 100644
--- a/update.sh
+++ b/update.sh
@@ -21,7 +21,7 @@ OS=$(lsb_release -si)
 OS_VER=$(lsb_release -sr)
 
 # Debian OS
-if [ -f /etc/debian_version ]; then
+if [ ${OS} == 'Debian' ] || [ ${OS} == 'Ubuntu' ]; then
     # upgrade all packages
     apt update; apt upgrade -y
     
@@ -52,7 +52,7 @@ if [ -f /etc/debian_version ]; then
     update-ca-certificates
 
 # CentOS OS
-elif [ -f /etc/redhat-release ]; then
+elif [ ${OS} == 'CentOS' ]; then
     # upgrade all packages
     yum update -y