diff --git a/web/includes/auth.php b/web/includes/auth.php
index d87e38d2b..fa3d5d3cc 100644
--- a/web/includes/auth.php
+++ b/web/includes/auth.php
@@ -364,7 +364,7 @@ function get_auth_relay() {
       return 'auth='.generateAuthHash(ZM_AUTH_HASH_IPS);
     } else if (ZM_AUTH_RELAY == 'plain') {
       // password probably needs to be escaped
-      return 'username='.$_SESSION['username'].'&password='.urlencode(isset($_SESSION['password']) ? $_SESSION['password'] : '');
+      return 'username='.(isset($_SESSION['username'])?$_SESSION['username']:'').'&password='.urlencode(isset($_SESSION['password']) ? $_SESSION['password'] : '');
     } else if (ZM_AUTH_RELAY == 'none') {
       return 'username='.$_SESSION['username'];
     } else {