diff --git a/backup.sh b/backup.sh
index f192f88..656dff4 100644
--- a/backup.sh
+++ b/backup.sh
@@ -11,7 +11,7 @@ fi
 # Chef if ATTACHMENT_BACKUP_FILE exist. If it's true, attechment are backup. We define var with or without TIMESTAMP
 # In anycase, we define var LOCALVAR_ATTACHMENT_BACKUP_FILE to limit the complexity of code (the number of if-else)
 LOCALVAR_ATTACHMENT_BACKUP_FILE = ""
-if [ -v ATTACHMENT_BACKUP_FILE ]
+if [ ! -z "${ATTACHMENT_BACKUP_FILE}" ]
 then
   LOCALVAR_ATTACHMENT_BACKUP_FILE = ${ATTACHMENT_BACKUP_FILE}
 fi
@@ -36,7 +36,7 @@ else
 fi
 
 
-if [ -v ATTACHMENT_BACKUP_FILE ]
+if [ ! -z "${ATTACHMENT_BACKUP_FILE}" ]
 then
   /bin/tar -cvzf ${FINAL_BACKUP_ATTACHMENT}.tgz ${ATTACHMENT_DIR}
 fi
@@ -45,7 +45,7 @@ if [ ! -z $DELETE_AFTER ] && [ $DELETE_AFTER -gt 0 ]
 then
   find $(dirname "$BACKUP_FILE") -name "$(basename "$BACKUP_FILE")*" -type f -mtime +$DELETE_AFTER -exec rm -f {} \; -exec echo "Deleted {} after $DELETE_AFTER days" \;
 
-  if [ -v ATTACHMENT_BACKUP_FILE ]
+  if [ ! -z "${ATTACHMENT_BACKUP_FILE}" ]
   then
     find $(dirname "$FINAL_BACKUP_ATTACHMENT") -name "$(basename "$FINAL_BACKUP_ATTACHMENT")*" -type f -mtime +$DELETE_AFTER -exec rm -f {} \; -exec echo "Deleted {} after $DELETE_AFTER days" \;
   fi