diff --git a/Network/Wai/Application/Classic/CGI.hs b/Network/Wai/Application/Classic/CGI.hs
--- a/Network/Wai/Application/Classic/CGI.hs
+++ b/Network/Wai/Application/Classic/CGI.hs
@@ -59,8 +59,8 @@
     fromCGI rhdl cspec req
   where
     register3 (rhdl,whdl,pid) = do
-        register $ terminateProcess pid -- SIGTERM
-        register $ hClose rhdl
+        _ <- register $ terminateProcess pid -- SIGTERM
+        _ <- register $ hClose rhdl
         keyw <- register $ hClose whdl
         return (rhdl,whdl,release keyw)
 
diff --git a/Network/Wai/Application/Classic/Conduit.hs b/Network/Wai/Application/Classic/Conduit.hs
--- a/Network/Wai/Application/Classic/Conduit.hs
+++ b/Network/Wai/Application/Classic/Conduit.hs
@@ -45,7 +45,7 @@
 keyVal :: Parser RequestHeader
 keyVal = do
     key <- takeTill (wcollon==)
-    word8 wcollon
+    _ <- word8 wcollon
     skipWhile (wspace ==)
     val <- takeTill (`elem` [wlf,wcr])
     crlf
diff --git a/Network/Wai/Application/Classic/Path.hs b/Network/Wai/Application/Classic/Path.hs
--- a/Network/Wai/Application/Classic/Path.hs
+++ b/Network/Wai/Application/Classic/Path.hs
@@ -8,11 +8,9 @@
   , isSuffixOf
   ) where
 
-import qualified Blaze.ByteString.Builder as BB
 import Data.ByteString (ByteString)
-import qualified Data.ByteString as BS (null, head, tail, last, append, drop, length, breakByte, isSuffixOf)
+import qualified Data.ByteString as BS (null, head, tail, last, concat, append, drop, length, breakByte, isSuffixOf)
 import qualified Data.ByteString.Char8 as BS (pack, unpack)
-import Data.Monoid
 import Data.String
 import Data.Word
 import Data.Function
@@ -45,12 +43,18 @@
   , pathByteString = path
   }
 
-pathDot :: Word8
-pathDot = 46
+-- pathDot :: Word8
+-- pathDot = 46
 
+pathDotBS :: ByteString
+pathDotBS = "."
+
 pathSep :: Word8
 pathSep = 47
 
+pathSepBS :: ByteString
+pathSepBS = "/"
+
 {-|
   Checking if the path ends with the path separator.
 
@@ -90,10 +94,7 @@
 -}
 
 (+++) :: Path -> Path -> Path
-p1 +++ p2 = Path {
-    pathString = BS.unpack p
-  , pathByteString = p
-  }
+p1 +++ p2 = fromByteString p
   where
     p = pathByteString p1 `BS.append` pathByteString p2
 
@@ -113,22 +114,15 @@
 (</>) :: Path -> Path -> Path
 p1 </> p2
   | has1 && not has2 || not has1 && has2 = p1 +++ p2
-  | has1      = toPath pp1
-  | otherwise = toPath pp2
+  | has1      = fromByteString pp1
+  | otherwise = fromByteString pp2
   where
     has1 = hasTrailingPathSeparator p1
     has2 = hasLeadingPathSeparator p2
     p1' = pathByteString p1
     p2' = pathByteString p2
-    toPath p = Path {
-        pathString = BS.unpack p
-      , pathByteString = p
-      }
-    pp1 = BB.toByteString (BB.fromByteString p1'
-                           `mappend` BB.fromByteString (BS.tail p2'))
-    pp2 = BB.toByteString (BB.fromByteString p1'
-                           `mappend` BB.fromWord8 pathSep
-                           `mappend` BB.fromByteString p2')
+    pp1 = p1' `BS.append` BS.tail p2'
+    pp2 = BS.concat [p1',pathSepBS,p2']
 
 {-|
   Removing prefix. The prefix of the second argument is removed
@@ -142,10 +136,7 @@
 "bar"
 -}
 (<\>) :: Path -> Path -> Path
-p1 <\> p2 = Path {
-    pathString = BS.unpack p
-  , pathByteString = p
-  }
+p1 <\> p2 = fromByteString p
   where
     p1' = pathByteString p1
     p2' = pathByteString p2
@@ -155,16 +146,11 @@
   Adding suffix.
 -}
 (<.>) :: Path -> Path -> Path
-p1 <.> p2 = Path {
-    pathString = BS.unpack p
-  , pathByteString = p
-  }
+p1 <.> p2 = fromByteString p
   where
     p1' = pathByteString p1
     p2' = pathByteString p2
-    p = BB.toByteString (BB.fromByteString p1'
-                       `mappend` BB.fromWord8 pathDot
-                       `mappend` BB.fromByteString p2')
+    p = BS.concat [p1',pathDotBS,p2']
 
 {-|
   Breaking at the first path separator.
diff --git a/wai-app-file-cgi.cabal b/wai-app-file-cgi.cabal
--- a/wai-app-file-cgi.cabal
+++ b/wai-app-file-cgi.cabal
@@ -1,5 +1,5 @@
 Name:                   wai-app-file-cgi
-Version:                0.5.9
+Version:                0.5.10
 Author:                 Kazu Yamamoto <kazu@iij.ad.jp>
 Maintainer:             Kazu Yamamoto <kazu@iij.ad.jp>
 License:                BSD3
@@ -13,10 +13,7 @@
 Build-Type:             Simple
 
 Library
-  if impl(ghc >= 6.12)
-    GHC-Options:        -Wall -fno-warn-unused-do-bind
-  else
-    GHC-Options:        -Wall
+  GHC-Options:          -Wall
   Exposed-Modules:      Network.Wai.Application.Classic
   Other-Modules:        Network.Wai.Application.Classic.CGI
                         Network.Wai.Application.Classic.Conduit