diff --git a/src/Lib/Prettier.idr b/src/Lib/Prettier.idr
index b0dc33a..cf99175 100644
--- a/src/Lib/Prettier.idr
+++ b/src/Lib/Prettier.idr
@@ -33,10 +33,10 @@ group : Doc -> Doc
 group x = Alt (flatten x) x
 
 -- TODO - we can accumulate snoc and cat all at once
-layout : List Item -> String
-layout [] = ""
-layout (LINE k :: x) = "\n" ++ replicate k ' ' ++ layout x
-layout (TEXT str :: x) = str ++ layout x
+layout : List Item -> SnocList String -> String
+layout [] acc = fastConcat $ cast acc
+layout (LINE k :: x) acc = layout x (acc :< "\n" :< replicate k ' ')
+layout (TEXT str :: x) acc = layout x (acc :< str)
 
 ||| Whether a documents first line fits.
 fits : Nat -> List Item -> Bool
@@ -73,7 +73,7 @@ interface Pretty a where
 
 export
 render : Nat -> Doc -> String
-render w x = layout (best w 0 x)
+render w x = layout (best w 0 x) [<]
 
 public export
 Semigroup Doc where x <+> y = Seq x (Seq (Text " ") y)
diff --git a/src/Main.idr b/src/Main.idr
index 4e70838..a9d281f 100644
--- a/src/Main.idr
+++ b/src/Main.idr
@@ -41,11 +41,11 @@ dumpContext top = do
 writeSource : String -> M ()
 writeSource fn = do
   docs <- compile
-  let src = unlines $ ["#!/usr/bin/env node"]
+  let src = unlines $
+        [ "#!/usr/bin/env node"
+        ,  "const PiType = (h0, h1) => ({ tag: \"PiType\", h0, h1 })" ]
         ++ map (render 90) docs
-        ++ [ "const PiType = (h0, h1) => ({ tag: \"PiType\", h0, h1 })"
-           , "main();"
-           ]
+        ++ [ "main();" ]
   Right _ <- writeFile fn src
     | Left err => fail (show err)
   Right _ <- chmodRaw fn 493 | Left err => fail (show err)