diff --git a/polyplate/Data/Generics/Polyplate/GenInstances.hs b/polyplate/Data/Generics/Polyplate/GenInstances.hs
index 9089347..fc50503 100644
--- a/polyplate/Data/Generics/Polyplate/GenInstances.hs
+++ b/polyplate/Data/Generics/Polyplate/GenInstances.hs
@@ -18,7 +18,7 @@ with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 module Data.Generics.Polyplate.GenInstances
   (GenOverlappedOption(..), GenClassOption(..),
-   genHeader, GenInstance, genInstance, genInstances,
+   GenInstance, genInstance, genInstances,
    writeInstances, writeInstancesTo) where
 
 import Control.Monad.State
@@ -35,18 +35,6 @@ data GenOverlappedOption = GenWithOverlapped | GenWithoutOverlapped
 data GenClassOption = GenClassPerType | GenOneClass | GenSlowDelegate
   deriving (Eq)
 
--- | Given the first line of the file (first parameter, which may be a directive
--- to GHC with some options), a module name (second parameter), generates a list
--- of lines that form the header of the module.  You can easily just write a similar
--- function yourself if you want more control over the comments.
-genHeader :: String -> String -> [String]
-genHeader firstLine moduleName
-  = [firstLine
-    ,"-- | Instances for Polyplate."
-    ,"-- This library was automatically generated by Data.Generics.Polyplate.GenInstances"
-    ,"-- and should NOT be edited directly."
-    ,"module " ++ moduleName ++ " where"]
-
 -- | A type that represents a generator for instances of a set of types.
 newtype GenInstance = GenInstance (TypeMapM ())
 
@@ -189,7 +177,7 @@ instancesFrom genOverlapped genClass@GenOneClass boxes w
             -- A primitive type: just return it.
             else ["  transformM () _ v = return v"]) ++
           [""
-          , "instance PolyplateM (" ++ wName ++ ") () () m where"
+          , "instance Monad m => PolyplateM (" ++ wName ++ ") () () m where"
           , "  transformM () () v = return v"
           ] ++
           if genOverlapped == GenWithoutOverlapped then [] else
@@ -272,20 +260,19 @@ genInstances op1 op2 insts
         liftM concat $ sequence [instancesFrom op1 op2 (justBoxes typeMap) w | DataBox w <- justBoxes typeMap]
 
 -- | Generates the instances according to the options and writes it to stdout with
--- the header for the given first line and module name.
-writeInstances :: GenOverlappedOption -> GenClassOption -> [GenInstance] -> String
-  -> String -> IO ()
-writeInstances op1 op2 inst firstLine moduleName
+-- the given header.
+writeInstances :: GenOverlappedOption -> GenClassOption -> [GenInstance] -> [String] -> IO ()
+writeInstances op1 op2 inst header
   = do instLines <- genInstances op1 op2 inst
-       putStr (unlines (genHeader firstLine moduleName ++ instLines))
+       putStr (unlines (header ++ instLines))
 
 -- | Generates the instances according to the options and writes it to a file with
--- the header and given module name.
-writeInstancesTo :: GenOverlappedOption -> GenClassOption -> [GenInstance] -> String
-  -> String -> FilePath -> IO ()
-writeInstancesTo op1 op2 inst firstLine moduleName fileName
+-- the given header.
+writeInstancesTo :: GenOverlappedOption -> GenClassOption -> [GenInstance] -> [String]
+  -> FilePath -> IO ()
+writeInstancesTo op1 op2 inst header fileName
   = do instLines <- genInstances op1 op2 inst
-       writeFile fileName (unlines (genHeader firstLine moduleName ++ instLines))
+       writeFile fileName (unlines (header ++ instLines))
 
 
 --{{{ Various SYB-based functions that we don't export, for discovering contained types:
diff --git a/pregen/GenNavAST.hs b/pregen/GenNavAST.hs
index 76f489c..f8970c0 100644
--- a/pregen/GenNavAST.hs
+++ b/pregen/GenNavAST.hs
@@ -19,16 +19,9 @@ with this program.  If not, see <http://www.gnu.org/licenses/>.
 -- | Utilities for metaprogramming.
 module GenNavAST where
 
-import Data.Char
-import Data.Generics
-import Data.List
-import qualified Data.Set as Set
-
 import Data.Generics.Polyplate.GenInstances
 
 import qualified AST
-import PregenUtils
-import Utils
 
 header :: [String]
 header
@@ -156,6 +149,14 @@ main :: IO ()
 main
   = writeInstances GenWithoutOverlapped GenOneClass
       [genInstance (undefined :: AST.AST)]
-      "{-# OPTIONS_GHC -Werror -fwarn-overlapping-patterns -fwarn-unused-matches -fwarn-unused-binds -fwarn-incomplete-patterns #-}"
-      "NavAST"
+      ["{-# OPTIONS_GHC -Werror -fwarn-overlapping-patterns -fwarn-unused-matches -fwarn-unused-binds -fwarn-incomplete-patterns #-}"
+      ,"-- | This module is auto-generated by Polyplate.  DO NOT EDIT."
+      ,"module NavAST where"
+      ,""
+      ,"import Data.Generics.Polyplate"
+      ,""
+      ,"import qualified AST"
+      ,"import qualified Metadata"
+      ,""
+      ]