[Haskell] A haddock question

Hello, I have a module with a public class plus some instances for public data types. In addition, I use this class inside another module where I declare local (module private) data types and make them instances of the class. I had expected that haddock (I am using 0.7) will list in the documentation only instances of data types that are exported, but instead all instances are listed. Is there a way to persuade haddock to list only instances of data types that are actually visible to the user? Ben