diff --git a/CRM/Core/BAO/CustomField.php b/CRM/Core/BAO/CustomField.php
index 2ca7070c76cb..644f16fcffe6 100644
--- a/CRM/Core/BAO/CustomField.php
+++ b/CRM/Core/BAO/CustomField.php
@@ -1070,11 +1070,16 @@ private static function formatDisplayValue($value, $field, $entityId = NULL) {
       case 'Radio':
       case 'CheckBox':
         if ($field['data_type'] == 'ContactReference' && (is_array($value) || is_numeric($value))) {
-          $displayNames = [];
-          foreach ((array) $value as $contactId) {
-            $displayNames[] = CRM_Core_DAO::getFieldValue('CRM_Contact_DAO_Contact', $contactId, 'display_name');
+          if (empty($value)) {
+            $display = '';
+          }
+          else {
+            $displayNames = [];
+            foreach ((array) $value as $contactId) {
+              $displayNames[] = CRM_Core_DAO::getFieldValue('CRM_Contact_DAO_Contact', $contactId, 'display_name');
+            }
+            $display = implode(', ', $displayNames);
           }
-          $display = implode(', ', $displayNames);
         }
         elseif ($field['data_type'] == 'ContactReference') {
           $display = $value;