diff --git a/api/src/Contacts/Ldap.php b/api/src/Contacts/Ldap.php
index a399fa1358..53c27c5778 100644
--- a/api/src/Contacts/Ldap.php
+++ b/api/src/Contacts/Ldap.php
@@ -974,7 +974,7 @@ class Ldap
 					break;
 
 				case 'list':
-					$filter .= $this->membershipFilter($value);
+					$filters .= $this->membershipFilter($value);
 					break;
 
 				default: