diff --git a/modules/monitoring/library/Monitoring/Backend/Ido/Query/NotificationhistoryQuery.php b/modules/monitoring/library/Monitoring/Backend/Ido/Query/NotificationhistoryQuery.php
index 1195161d3..8bbdc0751 100644
--- a/modules/monitoring/library/Monitoring/Backend/Ido/Query/NotificationhistoryQuery.php
+++ b/modules/monitoring/library/Monitoring/Backend/Ido/Query/NotificationhistoryQuery.php
@@ -26,6 +26,15 @@ class NotificationhistoryQuery extends IdoQuery
         )
     );
 
+    public function whereToSql($col, $sign, $expression)
+    {
+        if ($col === 'UNIX_TIMESTAMP(n.start_time)') {
+            return 'n.start_time ' . $sign . ' ' . $this->timestampForSql($this->valueToTimestamp($expression));
+        } else {
+            return parent::whereToSql($col, $sign, $expression);
+        }
+    }
+
     protected function joinBaseTables()
     {
         switch ($this->ds->getDbType()) {