diff --git a/addons/portal_anonymous/static/src/js/portal_anonymous.js b/addons/portal_anonymous/static/src/js/portal_anonymous.js
index 44f599b9fb6..875268be196 100644
--- a/addons/portal_anonymous/static/src/js/portal_anonymous.js
+++ b/addons/portal_anonymous/static/src/js/portal_anonymous.js
@@ -3,16 +3,24 @@ openerp.portal_anonymous = function(instance) {
     instance.web.Session.include({
         load_translations: function() {
             var self = this;
-            if (self.username === 'anonymous') {
-                self.user_context.lang = (navigator.language || navigator.userLanguage).replace('-', '_');
-                if (self.user_context.lang.length === 2) {
-                    return (new instance.web.Model('res.lang')).query(['code'])
-                        .filter([['iso_code', '=', self.user_context.lang]]).all()
-                        .then(function(result) {
-                            self.user_context.lang = result[0].code;
-                            return self._super();
-                        });
-                }
+            // browser_lang can contain 'xx' or 'xx_XX'
+            // we use the 'xx' to find matching languages installed in the DB
+            var browser_lang = (navigator.language || navigator.userLanguage).replace('-', '_');
+            // By default for anonymous session.user_context.lang === 'en_US',
+            // so do nothing if browser_lang is contained in 'en_US' (like 'en' or 'en_US')
+            if (this.username === 'anonymous' && this.user_context.lang.indexOf(browser_lang) === -1) {
+                return (new instance.web.Model('res.lang')).query(['code', 'iso_code'])
+                    .filter([['code', 'like', browser_lang.substring(0, 2).toLowerCase()]]).all()
+                .then(function(langs) {
+                    // If langs is empty (OpenERP doesn't support the language),
+                    // then don't change session.user_context.lang else take the
+                    // first returned language
+                    if (langs.length > 0) {
+                        self.user_context.lang = langs.sort(function(a, b) {
+                            return a.length - b.length;
+                        })[0].code;
+                    }
+                });
             }
             return self._super();
         },