diff --git a/lib/devise/parameter_sanitizer.rb b/lib/devise/parameter_sanitizer.rb
index 6e4bf074..7b10cf55 100644
--- a/lib/devise/parameter_sanitizer.rb
+++ b/lib/devise/parameter_sanitizer.rb
@@ -60,6 +60,8 @@ module Devise
 
     private
 
+    # TODO: We do need to flatten so it works with strong_parameters
+    # gem. We should drop it once we move to Rails 4 only support.
     def permit(keys)
       default_params.permit(*Array(keys))
     end