diff --git a/inc/drivers_ldap.php b/inc/drivers_ldap.php
index 7a616880..6ebbb0f6 100644
--- a/inc/drivers_ldap.php
+++ b/inc/drivers_ldap.php
@@ -598,7 +598,9 @@ function sync_LDAP_groups(){
   if ( sizeof ( $groups_to_update ) ){
     $c->messages[] = sprintf(i18n('- updating groups : %s'),join(', ',$groups_to_update));
     foreach ( $groups_to_update as $group ){
-      $db_members = array_values ( $db_group_members[$group] );
+      $db_members = is_array( $db_group_members[$group] )
+          ? array_values( $db_group_members[$group] )
+          : array();
       $ldap_members = array_values ( $ldap_groups_info[$group][$member_field] );
 
       $mapping_field = $c->authenticate_hook['config']['mapping_field'];