Hello Consider the following data, class and instance: class PP m where create :: a -> m a data A a = A a instance PP A where create a = A a And then: class CB a where fb :: a -> Int data B m a = B (m a) If I try to define an instance of PP for B with the following implementation: instance (PP m) => PP (B m) where create a = let _ = fb a in B (create a) GHC issues the (expected) error: Could not deduce (CB a) arising from a use of 'fb' from the context (PP m). So the workaround I am using is to define a new class PP' where the type a is made more explicit. That allows the constraint (CB a) to be stated in an instance declaration. class PP' m a where create' :: a -> m a instance (PP m) => PP' m a where create' = create instance (PP m, CB a) => PP' (B m) a where create' a = let _ = fb a in B (create a) So, my question is: is there a way to achieve the same results without having to create the new class PP'? Thank you for your help J-C