diff --git a/phpBB/includes/ucp/ucp_register.php b/phpBB/includes/ucp/ucp_register.php
index 2e962b55ea..1ef761eaab 100644
--- a/phpBB/includes/ucp/ucp_register.php
+++ b/phpBB/includes/ucp/ucp_register.php
@@ -363,7 +363,7 @@ class ucp_register
 					$config['require_activation'] == USER_ACTIVATION_SELF ||
 					$config['require_activation'] == USER_ACTIVATION_ADMIN) && $config['email_enable'])
 				{
-					$user_actkey = gen_rand_string(32);
+					$user_actkey = strtolower(gen_rand_string(32));
 					$user_type = USER_INACTIVE;
 					$user_inactive_reason = INACTIVE_REGISTER;
 					$user_inactive_time = time();