diff --git a/server/plugins-available/aps_plugin.inc.php b/server/plugins-available/aps_plugin.inc.php
index badbc0e61c946c61f4513bef64362661658d4a94..ddeca3d438ff0d6618ee645321906b89b7ed352c 100644
--- a/server/plugins-available/aps_plugin.inc.php
+++ b/server/plugins-available/aps_plugin.inc.php
@@ -28,7 +28,7 @@ NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
 EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
 
-if(defined(ISPC_ROOT_PATH)) include_once(ISPC_ROOT_PATH.'/lib/classes/aps_installer.inc.php');
+if(defined('ISPC_ROOT_PATH')) include_once(ISPC_ROOT_PATH.'/lib/classes/aps_installer.inc.php');
 //require_once(ISPC_ROOT_PATH.'/lib/classes/class.installer.php');
 
 class aps_plugin