diff --git a/bin/monitor.php b/bin/monitor.php
index febc9b38b..9ac6076d9 100755
--- a/bin/monitor.php
+++ b/bin/monitor.php
@@ -120,7 +120,7 @@ while($i>0)
 
   if ($i!=1) {
     sleep($array['MONITOR_UPDATE']);
-    $time_loop_start=$time_loop_start-$array['MONITOR_UPDATE'];
+    $time_loop_start=$time_loop_start+$array['MONITOR_UPDATE'];
   }
   $short_sleep = $array['MONITOR_UPDATE'];