diff --git a/class_appdb.php b/class_appdb.php
index 358a16d..8057e4c 100644
--- a/class_appdb.php
+++ b/class_appdb.php
@@ -12,7 +12,7 @@ class AppDB {
    private static $dbh = null;
 
    public static function getLastInsertId() {
-       if ( is_null($dbh) ) return 0;
+       if ( is_null(self::$dbh) ) return 0;
        return self::$dbh->lastInsertId();
    }