diff --git a/System/Console/Terminfo/PrettyPrint.hs b/System/Console/Terminfo/PrettyPrint.hs
--- a/System/Console/Terminfo/PrettyPrint.hs
+++ b/System/Console/Terminfo/PrettyPrint.hs
@@ -196,7 +196,8 @@
 kludgeWindowSize :: IO Int
 kludgeWindowSize = do
    _ <- initScr
-   snd <$> scrSize
+   s <- snd <$> scrSize
+   guard $ s >= 30 && s < 320
  `finally` endWin
 
 displayLn :: PrettyTerm t => t -> IO ()
@@ -245,7 +246,7 @@
 instance PrettyTerm Integer
 instance PrettyTerm Float
 instance PrettyTerm Double
-
+instance PrettyTerm ()
 instance (PrettyTerm a,PrettyTerm b) => PrettyTerm (a,b) where
   prettyTerm (x,y) = tupled [prettyTerm x, prettyTerm y]
 
diff --git a/wl-pprint-terminfo.cabal b/wl-pprint-terminfo.cabal
--- a/wl-pprint-terminfo.cabal
+++ b/wl-pprint-terminfo.cabal
@@ -1,6 +1,6 @@
 name:          wl-pprint-terminfo
 category:      Control, Monads, Text
-version:       0.4
+version:       0.5
 cabal-version: >= 1.6
 license:       BSD3
 license-file:  LICENSE