diff --git a/phpBB/includes/acp/acp_captcha.php b/phpBB/includes/acp/acp_captcha.php
index 57de03c4c9..f90699b2a8 100644
--- a/phpBB/includes/acp/acp_captcha.php
+++ b/phpBB/includes/acp/acp_captcha.php
@@ -79,7 +79,7 @@ class acp_captcha
 						$old_captcha->uninstall();
 						set_config('captcha_plugin', $selected);
 						$new_captcha = phpbb_captcha_factory::get_instance($config['captcha_plugin']);
-						$old_captcha->install();
+						$new_captcha->install();
 					}
 					else
 					{
diff --git a/phpBB/includes/captcha/plugins/captcha_abstract.php b/phpBB/includes/captcha/plugins/captcha_abstract.php
index 1b511b9c49..c8545cdd69 100644
--- a/phpBB/includes/captcha/plugins/captcha_abstract.php
+++ b/phpBB/includes/captcha/plugins/captcha_abstract.php
@@ -262,7 +262,7 @@ abstract class phpbb_default_captcha implements phpbb_captcha_plugin
 		global $db, $user;
 
 		$sql = 'DELETE FROM ' . CONFIRM_TABLE . "
-				WHERE confirm_id = '" . $db->sql_escape($confirm_id) . "'
+				WHERE confirm_id = '" . $db->sql_escape($this->confirm_id) . "'
 					AND session_id = '" . $db->sql_escape($user->session_id) . "'
 					AND confirm_type = " . $this->type;
 		$db->sql_query($sql);