diff --git a/lib/passport-saml/saml.js b/lib/passport-saml/saml.js
index 7873023a..9e5c4e5e 100644
--- a/lib/passport-saml/saml.js
+++ b/lib/passport-saml/saml.js
@@ -1249,7 +1249,10 @@ SAML.prototype.generateServiceProviderMetadata = function( decryptionCert, signi
     };
   }
 
-  metadata.EntityDescriptor.SPSSODescriptor.NameIDFormat = this.options.identifierFormat;
+  if (this.options.identifierFormat) {
+    metadata.EntityDescriptor.SPSSODescriptor.NameIDFormat = this.options.identifierFormat;
+  }
+
   metadata.EntityDescriptor.SPSSODescriptor.AssertionConsumerService = {
     '@index': '1',
     '@isDefault': 'true',