I've seen questions on using HStringTemplate with syb-with-class on the list before, but haven't seen this issue addressed. I'm hoping it's a noob issue, and, therefore, thought I would check with the list before spending too much time digging around for solutions. I'm attempting to use HStringTemplate with the syb-with-class support. I've made sure HStringTemplate is installed with 'syb-with-class=True'. 'genericToSElem' is always failing on the 'True =' guard with an error of "Unable to serialize the primitive type [...]" with whatever primitive Haskell type I've included in my ADT; for example, "Unable to serialize the primitive type 'Prelude.Int'". I've made sure to include 'Text.StringTemplate.GenericWithClass', 'Data.Generics.SYB.WithClass.Basics', and 'Data.Generics.SYB.WithClass.Derive', and to derive instances of the 'Typeable' and 'Data' classes with '$(derive [''Test])', where 'Test' is my test ADT. This makes me think that the overloaded 'toSElem' functions defined by the instances in 'Text.StringTemplate.Instances' are not being called? A cursory comparison to RJson, which the HStringTemplate syb-with-class solution is based on, didn't lead me to any obvious differences that I was missing. For reference, my current configuration is (Sorry, it's an older configuration, but the one I'm stuck with for now) GHC 6.10.4 (Mac OS X 10.6.4, Intel) HStringTemplate 0.6.3 syb-with-class 0.6