diff --git a/javascript/i18n/phonenumbers/phonenumberutil.js b/javascript/i18n/phonenumbers/phonenumberutil.js
index d530dae5e..ba427426a 100644
--- a/javascript/i18n/phonenumbers/phonenumberutil.js
+++ b/javascript/i18n/phonenumbers/phonenumberutil.js
@@ -4760,7 +4760,7 @@ i18n.phonenumbers.PhoneNumberUtil.prototype.canBeInternationallyDialled =
 i18n.phonenumbers.PhoneNumberUtil.matchesEntirely = function(regex, str) {
   /** @type {Array.<string>} */
   var matchedGroups = (typeof regex == 'string') ?
-      str.match('^(?:' + regex + ')$') : str.match(regex);
+      str.match('^(?:' + regex + ')$') : str.match("^(?:" + regex.source + ")$");
   if (matchedGroups && matchedGroups[0].length == str.length) {
     return true;
   }