diff --git a/auth.php b/auth.php
index 3eb5441..b7dae67 100644
--- a/auth.php
+++ b/auth.php
@@ -142,6 +142,7 @@ class auth_plugin_crewauth extends auth_plugin_base {
             $user = $DB->get_record('user', array('username'=>(string)(int)$_POST["username"], 'mnethostid'=>$CFG->mnet_localhost_id));
             $user->auth = $this->authtype;
             $DB->update_record("user", $user, $bulk=false);
+            $_POST["username"] = (string)(int)$_POST["username"];
         }
     }