[Haskell-cafe] Obscure instances for Obscure types

Hi I currently maintain two libraries, TagSoup which defines the Tag data type, and BinaryDefer, which defines the BinaryDefer class. If I wanted to include an instance for BinaryDefer Tag, where would I put it? Putting it in either library introduces an artificial dependency on the other. Putting it in a separate libary makes the library about 4 lines long and is just annoying. Putting it in the individual application(s) is exactly what libraries were designed to avoid. Is there a solution? Thanks Neil