diff --git a/app/controllers/application_controller.rb b/app/controllers/application_controller.rb
index b398d5420..e070d438c 100644
--- a/app/controllers/application_controller.rb
+++ b/app/controllers/application_controller.rb
@@ -133,7 +133,14 @@ def has_access?
 
   def set_locale
     store_locale_to_cookie(params[:locale]) if locale
-    I18n.locale = cookies[:locale] || I18n.default_locale
+    I18n.locale = locale_value
+  end
+
+  def locale_value
+    return I18n.default_locale unless cookies[:locale].present?
+    return I18n.default_locale unless I18n.available_locales.include?(cookies[:locale].to_sym)
+
+    cookies[:locale]
   end
 
   def user_not_authorized