diff --git a/lib/os.lib.sh b/lib/os.lib.sh
index 3972114..48ea6a5 100644
--- a/lib/os.lib.sh
+++ b/lib/os.lib.sh
@@ -19,23 +19,23 @@ zaf_configure_os_freebsd() {
 zaf_detect_system() {
 	if which dpkg >/dev/null; then
 		ZAF_PKG=dpkg
-		ZAF_OS=$(lsb_release -is|tr '[:upper:]' '[:lower:]')
-		ZAF_OS_CODENAME=$(lsb_release -cs|tr '[:upper:]' '[:lower:]')
+		ZAF_OS=$(lsb_release -is|zaf_tolower)
+		ZAF_OS_CODENAME=$(lsb_release -cs|zaf_tolower)
 		ZAF_CURL_INSECURE=0
 		ZAF_AGENT_PKG="zabbix-agent"
 		return
 	else if which rpm >/dev/null; then
 		ZAF_PKG="rpm"
-		ZAF_OS=$(lsb_release -is|tr '[:upper:]' '[:lower:]')
-		ZAF_OS_CODENAME=$(lsb_release -cs|tr '[:upper:]' '[:lower:]')
+		ZAF_OS=$(lsb_release -is|zaf_tolower)
+		ZAF_OS_CODENAME=$(lsb_release -cs|zaf_tolower)
 		ZAF_CURL_INSECURE=0
 		ZAF_AGENT_PKG="zabbix-agent"
 		return
 	else if which opkg >/dev/null; then
 		ZAF_PKG="opkg"
 		. /etc/openwrt_release
-		ZAF_OS="$(echo $DISTRIB_ID|tr '[:upper:]' '[:lower:]')"
-		ZAF_OS_CODENAME="$(echo $DISTRIB_CODENAME|tr '[:upper:]' '[:lower:]')"
+		ZAF_OS="$(echo $DISTRIB_ID|zaf_tolower)"
+		ZAF_OS_CODENAME="$(echo $DISTRIB_CODENAME|zaf_tolower)"
 		return	
 	else if which pkg >/dev/null; then
 		ZAF_PKG="pkg"
diff --git a/lib/zaf.lib.sh b/lib/zaf.lib.sh
index b0c90f3..00d74f7 100644
--- a/lib/zaf.lib.sh
+++ b/lib/zaf.lib.sh
@@ -340,4 +340,11 @@ zaf_remove_plugin() {
 	rm -f ${ZAF_AGENT_CONFIGD}/zaf_${plugin}.conf
 }
 
+zaf_tolower() {
+	tr 'ABCDEFGHIJKLMNOPQRSTUVWXYZ' 'abcdefghijklmnopqrstuvwxyz'
+}
+
+zaf_toupper() {
+	tr 'abcdefghijklmnopqrstuvwxyz' 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
+}