diff --git a/app/helpers/application_helper.rb b/app/helpers/application_helper.rb
index 5159635e..f8218a84 100644
--- a/app/helpers/application_helper.rb
+++ b/app/helpers/application_helper.rb
@@ -51,6 +51,7 @@ module ApplicationHelper
   end
 
   def gravatar_url(user)
+    return '//www.gravatar.com/avatar' if user.nil?
     "//www.gravatar.com/avatar/#{Digest::MD5.hexdigest(user.email)}"
   end
 end