diff --git a/phpBB/includes/ucp/ucp_register.php b/phpBB/includes/ucp/ucp_register.php
index 1ee3147072..793f5542f9 100644
--- a/phpBB/includes/ucp/ucp_register.php
+++ b/phpBB/includes/ucp/ucp_register.php
@@ -413,7 +413,7 @@ class ucp_register
 				$user_id = user_add($user_row, $cp_data);
 
 				// This should not happen, because the required variables are listed above...
-				if ($user_id === false)
+				if ((bool) $user_id === false)
 				{
 					trigger_error('NO_USER', E_USER_ERROR);
 				}