diff --git a/lib/omniauth/strategies/createsend.rb b/lib/omniauth/strategies/createsend.rb
index 0ae5013..5f85e3b 100644
--- a/lib/omniauth/strategies/createsend.rb
+++ b/lib/omniauth/strategies/createsend.rb
@@ -9,6 +9,10 @@ class CreateSend < OmniAuth::Strategies::OAuth2
         :authorize_url => "/oauth",
         :token_url => "/oauth/token"
       }
+
+      def callback_url
+        full_host + script_name + callback_path
+      end
     end
   end
 end