[Haskell-cafe] HSTringTemplate and syb-with-class

Hello all, I'm trying to use the generic capabilities of HSTringTemplate. The documentation claims that the package is able to automatically generate instances of ToSElem if syb-with-class is installed but gives no further details. I installed syb-with-class and then installed HSTringTemplate with additional configure parameter syb-with-class=True. But when I import Text.StringTemplate.GenericWithClass and then try deriving ToSElem or $(derive ToSElem), I just get an error like "Can't make a derived instance of `ToSElem ...". Any suggestions or pointer to further docs? Kind regards Torsten