diff --git a/security/Authenticator.php b/security/Authenticator.php
index 19f280d59..501f4a499 100644
--- a/security/Authenticator.php
+++ b/security/Authenticator.php
@@ -172,7 +172,7 @@ abstract class Authenticator extends SS_Object {
 	/**
 	 * Set a default authenticator (shows first in tabs)
 	 *
-	 * @param string
+	 * @param string $authenticator
 	 */
 	public static function set_default_authenticator($authenticator) {
 		self::$default_authenticator = $authenticator;