Hello! The attached code shows a behaviour which I don't understand. This could be a bug in TH or a misunderstanding on my side. The problem is that dynamically bound Names made with mkName sometimes "don't see" the variable. See the code for details. It could be a bit shorter, but I wanted to show why I cat't use the 'var syntax. Try to --make T, then uncomment the marked line in T.hs . Best regards Tomasz