diff --git a/check_systemd_service.sh b/check_systemd_service.sh
index c13bce4..7e2fab1 100644
--- a/check_systemd_service.sh
+++ b/check_systemd_service.sh
@@ -1,6 +1,6 @@
 #!/bin/bash
 
-# Copyright (C) 2016 Mohamed El Morabity <melmorabity@fedoraproject.com>
+# Copyright © 2016, 2017 Mohamed El Morabity <melmorabity@fedoraproject.com>
 #
 # This module is free software: you can redistribute it and/or modify it under
 # the terms of the GNU General Public License as published by the Free Software
@@ -19,8 +19,8 @@ PLUGINDIR=$(dirname $0)
 . $PLUGINDIR/utils.sh
 
 
-if [ $# -ne 1 ]; then
-    echo "Usage: ${0##*/} <service name>" >&2
+if [[ $# -ne 1 ]]; then
+    echo "Usage: ${0##*/} <service name>"
     exit $STATE_UNKNOWN
 fi
 
@@ -29,19 +29,19 @@ service=$1
 
 status=$(systemctl is-enabled $service 2>/dev/null)
 r=$?
-if [ -z "$status" ]; then
+if [[ -z "$status" ]]; then
     echo "ERROR: service $service doesn't exist"
     exit $STATE_CRITICAL
 fi
 
-if [ $r -ne 0 ]; then
+if [[ $r -ne 0 ]]; then
     echo "ERROR: service $service is $status"
     exit $STATE_CRITICAL
 fi
 
 
 systemctl --quiet is-active $service
-if [ $? -ne 0 ]; then
+if [[ $? -ne 0 ]]; then
     echo "ERROR: service $service is not running"
     exit $STATE_CRITICAL
 fi