diff --git a/htdocs/core/customreports.php b/htdocs/core/customreports.php
index 9498ed91d9c..d6e4f788500 100644
--- a/htdocs/core/customreports.php
+++ b/htdocs/core/customreports.php
@@ -390,6 +390,7 @@ if ($action == 'viewgraph') {
 // Get all possible values of fields when a 'group by' is set, and save this into $arrayofvaluesforgroupby
 // $arrayofvaluesforgroupby will be used to forge lael of each grouped series
 if (is_array($search_groupby) && count($search_groupby)) {
+	$fieldtocount = '';
 	foreach ($search_groupby as $gkey => $gval) {
 		$gvalwithoutprefix = preg_replace('/^[a-z]+\./', '', $gval);