diff --git a/phpBB/includes/acp/acp_groups.php b/phpBB/includes/acp/acp_groups.php
index 83c355540e..9b9ea38e07 100644
--- a/phpBB/includes/acp/acp_groups.php
+++ b/phpBB/includes/acp/acp_groups.php
@@ -80,6 +80,11 @@ class acp_groups
 			case 'approve':
 			case 'demote':
 			case 'promote':
+				if (!check_form_key($form_key))
+				{
+					trigger_error($user->lang['FORM_INVALID'] . adm_back_link($this->u_action), E_USER_WARNING);
+				}
+
 				if (!$group_id)
 				{
 					trigger_error($user->lang['NO_GROUP'] . adm_back_link($this->u_action), E_USER_WARNING);
@@ -252,6 +257,11 @@ class acp_groups
 			break;
 
 			case 'addusers':
+				if (!check_form_key($form_key))
+				{
+					trigger_error($user->lang['FORM_INVALID'] . adm_back_link($this->u_action), E_USER_WARNING);
+				}
+
 				if (!$group_id)
 				{
 					trigger_error($user->lang['NO_GROUP'] . adm_back_link($this->u_action), E_USER_WARNING);