diff --git a/CRM/Contact/BAO/Query.php b/CRM/Contact/BAO/Query.php
index 139b41619c27..4260a34ec549 100644
--- a/CRM/Contact/BAO/Query.php
+++ b/CRM/Contact/BAO/Query.php
@@ -5504,7 +5504,7 @@ public function ageRangeQueryBuilder(
 
     $asofDateValues = $this->getWhereValues("{$fieldName}_asof_date", $grouping);
     // will be treated as current day
-    $asofDate = NULL;
+    $asofDate = '';
     if ($asofDateValues) {
       $asofDate = CRM_Utils_Date::processDate($asofDateValues[2]);
       $asofDateFormat = CRM_Utils_Date::customFormat(substr($asofDate, 0, 8));