diff --git a/lib/validation.js b/lib/validation.js
index bea2db7..13269c9 100644
--- a/lib/validation.js
+++ b/lib/validation.js
@@ -21,13 +21,15 @@
 const isMobilePhone = require('validator/lib/isMobilePhone');
 
 module.exports = function telephoneValidation(input, settings) {
-  const set = settings;
+  // disable eslint for var because this is a browser-bound script
+  var locale = 'en-US'; // eslint-disable-line no-var
 
-  if (!set.hasOwnProperty('target') || !set.target.hasOwnProperty('locale') || set.target.locale === '') {
-    set.target.locale = 'en-US';
+  // check settings for locale
+  if (settings.hasOwnProperty('target') && settings.target.hasOwnProperty('locale') && settings.target.locale !== '' && typeof settings.target.locale === 'string') {
+    locale = settings.target.locale;
   }
 
-  if (input.target.value && !isMobilePhone(input.target.value, set.target.locale)) {
+  if (input.target.value && !isMobilePhone(input.target.value, locale)) {
     return `${input.target.name} must be a phone number`;
   }