diff --git a/gulliver/system/class.bootstrap.php b/gulliver/system/class.bootstrap.php
index ded3741cc..71f26ab1e 100644
--- a/gulliver/system/class.bootstrap.php
+++ b/gulliver/system/class.bootstrap.php
@@ -469,6 +469,10 @@ class Bootstrap
 	 * return true if the file exists, otherwise false.
 	 */
 	public function isPMUnderUpdating($setFlag = 2) {
+                if (!defined('PATH_DATA')) {
+                    return false;
+                }
+
 		$fileCheck = PATH_DATA . "UPDATE.dat";
 		if ($setFlag == 0) {
 			if (file_exists ( $fileCheck )) {