diff --git a/lib/types/string.js b/lib/types/string.js
index ba5650ef..f7a8fa45 100755
--- a/lib/types/string.js
+++ b/lib/types/string.js
@@ -286,7 +286,7 @@ module.exports = Any.extend({
         email: {
             method(options = {}) {
 
-                Common.assertOptions(options, ['allowFullyQualified', 'allowUnicode', 'ignoreLength', 'maxDomainSegments', 'minDomainSegments', 'multiple', 'separator', 'tlds']);
+                Common.assertOptions(options, ['allowFullyQualified', 'allowUnderscore', 'allowUnicode', 'ignoreLength', 'maxDomainSegments', 'minDomainSegments', 'multiple', 'separator', 'tlds']);
                 assert(options.multiple === undefined || typeof options.multiple === 'boolean', 'multiple option must be an boolean');
 
                 const address = internals.addressOptions(options);