diff --git a/bin/vmail-aliases-add.sh b/bin/vmail-aliases-add.sh
index 0739835..41097ac 100755
--- a/bin/vmail-aliases-add.sh
+++ b/bin/vmail-aliases-add.sh
@@ -49,14 +49,14 @@ fi
 
 # get mbox id, which also verfies that email address exists
 mbox_id=`mysql --defaults-extra-file=$MYSQL_CONNECTION_INFO_FILE -s -r -N -e "SELECT id FROM vm_mboxes WHERE domain_id='$domain_id' AND mbox='$mbox';"`
-if [ -z $mbox_id ] ; then
+if [[ -z $mbox_id ]]; then
   # mbox does not exist, can't create alias
   echo "ERROR: Address to Alias To ($email) does not exist."
   exit 1
-elif [ "$mbox_id" -gt '1' ] ; then
+elif [[ $mbox_id -gt 0 ]]; then
   # verified mbox, check for existing alias
   existing_alias=`mysql --defaults-extra-file=$MYSQL_CONNECTION_INFO_FILE -s -r -N -e "SELECT vm_aliases.id FROM vm_aliases WHERE vm_aliases.alias='$alias' AND vm_aliases.mbox_id='$mbox_id';"`
-  if [ -z $existing_alias ]; then
+  if [[ -z $existing_alias ]]; then
     # existing alias does not exist, add new one now
     dbcmd="mysql --defaults-extra-file=$MYSQL_CONNECTION_INFO_FILE -e 'INSERT INTO vm_aliases SET vm_aliases.alias=\"$alias\", vm_aliases.mbox_id=\"$mbox_id\";'"
     eval $dbcmd