diff --git a/CRM/Case/BAO/Case.php b/CRM/Case/BAO/Case.php
index bda424a9eff9..d936c32c3bf0 100644
--- a/CRM/Case/BAO/Case.php
+++ b/CRM/Case/BAO/Case.php
@@ -1141,6 +1141,7 @@ public static function getRelatedContacts($caseID, $includeDetails = TRUE) {
     }
 
     $values = [];
+    $caseClientCondition = !empty($caseInfo['client_id']) ? "AND cc.id NOT IN (%2)" : '';
     $query = <<<HERESQL
     SELECT cc.display_name as name, cc.sort_name as sort_name, cc.id, cr.relationship_type_id, crt.label_b_a as role, crt.name_b_a as role_name, crt.name_a_b as role_name_reverse, ce.email, cp.phone
     FROM civicrm_relationship cr
@@ -1157,7 +1158,7 @@ public static function getRelatedContacts($caseID, $includeDetails = TRUE) {
      AND cp.is_primary= 1
     WHERE cr.case_id =  %1
      AND cr.is_active
-     AND cc.id NOT IN (%2)
+     {$caseClientCondition}
     UNION
     SELECT cc.display_name as name, cc.sort_name as sort_name, cc.id, cr.relationship_type_id, crt.label_a_b as role, crt.name_a_b as role_name, crt.name_b_a as role_name_reverse, ce.email, cp.phone
     FROM civicrm_relationship cr
@@ -1174,12 +1175,15 @@ public static function getRelatedContacts($caseID, $includeDetails = TRUE) {
      AND cp.is_primary= 1
     WHERE cr.case_id =  %1
      AND cr.is_active
-     AND cc.id NOT IN (%2)
+     {$caseClientCondition}
 HERESQL;
     $params = [
       1 => [$caseID, 'Integer'],
-      2 => [implode(',', $caseInfo['client_id']), 'String'],
     ];
+
+    if ($caseClientCondition) {
+      $params[2] = [implode(',', $caseInfo['client_id']), 'CommaSeparatedIntegers'];
+    }
     $dao = CRM_Core_DAO::executeQuery($query, $params);
 
     while ($dao->fetch()) {