diff --git a/modules/saml/lib/IdP/SAML2.php b/modules/saml/lib/IdP/SAML2.php
index 243ae742fe..3a5ae0fbff 100644
--- a/modules/saml/lib/IdP/SAML2.php
+++ b/modules/saml/lib/IdP/SAML2.php
@@ -623,6 +623,7 @@ private static function generateNameIdValue(SimpleSAML_Configuration $idpMetadat
 			if ($attribute === NULL) {
 				if (!isset($state['UserID'])) {
 					SimpleSAML_Logger::error('Unable to generate NameID. Check the userid.attribute option.');
+					return NULL;
 				}
 				$attributeValue = $state['UserID'];
 				$idpEntityId = $idpMetadata->getString('entityid');