Hi Why is that Happstack has: instance Happstack.Data.Default.Default Data.ByteString But not one for: instance Happstack.Data.Default.Default Data.ByteString.Lazy I am trying to make a HTTP proxy using Happstack and the client part with the Network.HTTP (see Hackage). Network.HTTP.simpleHttp returns a lazy Bytestring when given a lazy Bytestring (which makes sense). Happstack on the other hand contains a lazy ByteString in its request type: data Request = Request { ... rqHeaders :: Headers, ... rqBody :: RqBody ... } newtype RqBody = Body Data.ByteString.Lazy.Internal.ByteString which Happstack.Server.SimpleHttp.simpleHTTP feeds into my application. However Happstack.Server.SimpleHttp.simpleHTTP expects something returned which is an instance of Happstack.Data.Default.Default which lazy ByteString is not. Confused? So am I. Who thought String handling could be so complex. Greetings, Mads Lindstrøm