diff --git a/modules/core/www/as_login.php b/modules/core/www/as_login.php
index 9fcd6ba8a5042e4739bc857f624e107a907e0899..189e05408248feb7d159db21028cd7774a563784 100644
--- a/modules/core/www/as_login.php
+++ b/modules/core/www/as_login.php
@@ -6,11 +6,11 @@
  * @package SimpleSAMLphp
  */
 
-if (!is_string($_REQUEST['ReturnTo'])) {
+if (!isset($_REQUEST['ReturnTo'])) {
 	throw new SimpleSAML_Error_BadRequest('Missing ReturnTo parameter.');
 }
 
-if (!is_string($_REQUEST['AuthId'])) {
+if (!isset($_REQUEST['AuthId'])) {
 	throw new SimpleSAML_Error_BadRequest('Missing AuthId parameter.');
 }