printf too strict?

I'm seeing more strictness than I'd expect for printf: > printf "foo %s\n" (show ([1..10] ++ undefined)) foo *** Exception: Prelude.undefined In contrast, *Utils.Fabprim.ToHaskell> "foo " ++ show ([1..10] ++ undefined) ++ "\n" "foo [1,2,3,4,5,6,7,8,9,10*** Exception: Prelude.undefined Known issue? -- Conal