diff --git a/auth/cas/auth.php b/auth/cas/auth.php
index ee9610abf85..ee3e72a675f 100644
--- a/auth/cas/auth.php
+++ b/auth/cas/auth.php
@@ -58,7 +58,7 @@ class auth_plugin_cas extends auth_plugin_base {
      */
     function user_login ($username, $password) {
 		$this->connectCAS();
-		return phpCAS::isAuthenticated() && (phpCAS::getUser() == $username);
+		return phpCAS::isAuthenticated() && (trim(moodle_strtolower(phpCAS::getUser())) == $username);
     }
     /**
      * Returns true if this authentication plugin is 'internal'.