Something strange happened and the body of my previous email was lost. I've re-sent it here. The attachments are there. http://www.haskell.org/pipermail/glasgow-haskell-users/2008-June/014973.html ===== Hi, I'm seeing the following bug revived in 6.8.2 and 6.8.3: http://hackage.haskell.org/trac/ghc/ticket/672 I use a default definition for class method, one that calls methods of dependent (super?) classes. Of course I'm embarrassed it took me so long to realize I didn't _need_ the class in the first place, I could just write a plain polymorphic function that calls those methods. Regardless, looks like a bug to me. Two files are attached, Test.hs and Vec.hs. Search for "BUG IS HERE" in Test.hs. There is a class and an instance declaration. Compile as-is to see the correct result. Comment out the method definition in the instance declaration to see the bug. If someone confirms, I'll open a ticket. Scott