diff --git a/hinstaller.cabal b/hinstaller.cabal
--- a/hinstaller.cabal
+++ b/hinstaller.cabal
@@ -1,6 +1,6 @@
 name: hinstaller
-version: 2007.4.24
-stability: Alpha
+version: 2007.5.13
+stability: Beta
 copyright: Matthew Sackman
 category: System
 maintainer: matthew@wellquite.org
diff --git a/src/System/Installer.hs b/src/System/Installer.hs
--- a/src/System/Installer.hs
+++ b/src/System/Installer.hs
@@ -67,7 +67,7 @@
 --    exports a function 'cabalCleanHInstallerDir'. To use this, modify
 --    your @Setup.hs@ along the lines of the following:
 --
--- >  #!\/usr\/bin\/env runghc
+-- >  #!/usr/bin/env runghc
 -- >
 -- >  import Distribution.Simple
 -- >  import System.Installer
@@ -99,7 +99,7 @@
                           binariesWithTmp
          ; func <- TH.makeInstallFunc funcName clauses
          ; dataDecls <- TH.makeDataDecls funcName binaries
-         ; return $ (concat importDecls) ++ (func : dataDecls)
+         ; return $ (concat importDecls) ++ func ++ dataDecls
          }
     where
       clauses = map (TH.makeInstallFuncCase funcName) binaries
diff --git a/src/System/Installer/TH.hs b/src/System/Installer/TH.hs
--- a/src/System/Installer/TH.hs
+++ b/src/System/Installer/TH.hs
@@ -45,9 +45,22 @@
       ptr = varE $ mkName ("installer_" ++ fullName)
       len = varE $ mkName ("installer_" ++ fullName ++ "_length")
 
-makeInstallFunc :: String -> [Q Clause] -> Q Dec
+makeInstallFunc :: String -> [Q Clause] -> Q [Dec]
 makeInstallFunc funcName clauses
-    = funD (mkName funcName) clauses
+    = do { func <- funD name clauses
+         ; funcSig <- sigD name (appT
+                                 (appT arrowT (conT dataDeclName))
+                                 (appT
+                                  (appT arrowT (conT fpName))
+                                  (appT (conT ioName) (conT tupName))))
+         ; return [funcSig, func]
+         }
+    where
+      name = mkName funcName
+      dataDeclName = mkName $ "Installer_" ++ funcName
+      fpName = mkName "FilePath"
+      ioName = mkName "IO"
+      tupName = mkName "()"
 
 makeDataDecls :: String -> [(String, FilePath)] -> Q [Dec]
 makeDataDecls base names