diff --git a/Network/Socket/Win32/Cmsg.hsc b/Network/Socket/Win32/Cmsg.hsc
index 702be7c1..435470ab 100644
--- a/Network/Socket/Win32/Cmsg.hsc
+++ b/Network/Socket/Win32/Cmsg.hsc
@@ -1,7 +1,8 @@
-
 {-# LANGUAGE AllowAmbiguousTypes #-}
 {-# LANGUAGE CPP #-}
+{-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
+{-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE PatternSynonyms #-}
 {-# LANGUAGE RecordWildCards #-}
 {-# LANGUAGE ScopedTypeVariables #-}
@@ -70,8 +71,8 @@ pattern CmsgIdIPv6PktInfo = CmsgId (#const IPPROTO_IPV6) (#const IPV6_PKTINFO)
 -- | Control message ID for POSIX file-descriptor passing.
 --
 --  Not supported on Windows; use WSADuplicateSocket instead
-pattern CmsgIdFd :: CmsgId
-pattern CmsgIdFd = CmsgId (-1) (-1)
+pattern CmsgIdFds :: CmsgId
+pattern CmsgIdFds = CmsgId (-1) (-1)
 
 ----------------------------------------------------------------
 
@@ -91,11 +92,13 @@ filterCmsg cid cmsgs = filter (\cmsg -> cmsgId cmsg == cid) cmsgs
 ----------------------------------------------------------------
 
 -- | A class to encode and decode control message.
-class Storable a => ControlMessage a where
+class ControlMessage a where
     controlMessageId :: CmsgId
+    encodeCmsg :: a -> Cmsg
+    decodeCmsg :: Cmsg -> Maybe a
 
-encodeCmsg :: forall a. ControlMessage a => a -> Cmsg
-encodeCmsg x = unsafeDupablePerformIO $ do
+encodeStorableCmsg :: forall a. (ControlMessage a, Storable a) => a -> Cmsg
+encodeStorableCmsg x = unsafeDupablePerformIO $ do
     bs <- create siz $ \p0 -> do
         let p = castPtr p0
         poke p x
@@ -104,8 +107,8 @@ encodeCmsg x = unsafeDupablePerformIO $ do
   where
     siz = sizeOf x
 
-decodeCmsg :: forall a . (ControlMessage a, Storable a) => Cmsg -> Maybe a
-decodeCmsg (Cmsg cmsid (PS fptr off len))
+decodeStorableCmsg :: forall a . (ControlMessage a, Storable a) => Cmsg -> Maybe a
+decodeStorableCmsg (Cmsg cmsid (PS fptr off len))
   | cid /= cmsid = Nothing
   | len < siz    = Nothing
   | otherwise = unsafeDupablePerformIO $ withForeignPtr fptr $ \p0 -> do
@@ -122,6 +125,8 @@ newtype IPv4TTL = IPv4TTL DWORD deriving (Eq, Show, Storable)
 
 instance ControlMessage IPv4TTL where
     controlMessageId = CmsgIdIPv4TTL
+    decodeCmsg = decodeStorableCmsg
+    encodeCmsg = encodeStorableCmsg
 
 ----------------------------------------------------------------
 
@@ -130,6 +135,8 @@ newtype IPv6HopLimit = IPv6HopLimit DWORD deriving (Eq, Show, Storable)
 
 instance ControlMessage IPv6HopLimit where
     controlMessageId = CmsgIdIPv6HopLimit
+    encodeCmsg = encodeStorableCmsg
+    decodeCmsg = decodeStorableCmsg
 
 ----------------------------------------------------------------
 
@@ -138,6 +145,8 @@ newtype IPv4TOS = IPv4TOS DWORD deriving (Eq, Show, Storable)
 
 instance ControlMessage IPv4TOS where
     controlMessageId = CmsgIdIPv4TOS
+    encodeCmsg = encodeStorableCmsg
+    decodeCmsg = decodeStorableCmsg
 
 ----------------------------------------------------------------
 
@@ -146,6 +155,8 @@ newtype IPv6TClass = IPv6TClass DWORD deriving (Eq, Show, Storable)
 
 instance ControlMessage IPv6TClass where
     controlMessageId = CmsgIdIPv6TClass
+    encodeCmsg = encodeStorableCmsg
+    decodeCmsg = decodeStorableCmsg
 
 ----------------------------------------------------------------
 
@@ -158,6 +169,8 @@ instance Show IPv4PktInfo where
 
 instance ControlMessage IPv4PktInfo where
     controlMessageId = CmsgIdIPv4PktInfo
+    encodeCmsg = encodeStorableCmsg
+    decodeCmsg = decodeStorableCmsg
 
 instance Storable IPv4PktInfo where
     sizeOf    ~_ = #{size IN_PKTINFO}
@@ -180,6 +193,8 @@ instance Show IPv6PktInfo where
 
 instance ControlMessage IPv6PktInfo where
     controlMessageId = CmsgIdIPv6PktInfo
+    decodeCmsg = decodeStorableCmsg
+    encodeCmsg = encodeStorableCmsg
 
 instance Storable IPv6PktInfo where
     sizeOf    ~_ = #{size IN6_PKTINFO}
@@ -192,8 +207,14 @@ instance Storable IPv6PktInfo where
         n :: ULONG  <- (#peek IN6_PKTINFO, ipi6_ifindex) p
         return $ IPv6PktInfo (fromIntegral n) ha6
 
-instance ControlMessage Fd where
-    controlMessageId = CmsgIdFd
+----------------------------------------------------------------
+
+instance ControlMessage [Fd] where
+    controlMessageId = CmsgIdFds
+    encodeCmsg = \_ -> Cmsg CmsgIdFds ""
+    decodeCmsg = \_ -> Just []
+
+----------------------------------------------------------------
 
 cmsgIdBijection :: Bijection CmsgId String
 cmsgIdBijection =
@@ -204,7 +225,7 @@ cmsgIdBijection =
     , (CmsgIdIPv6TClass, "CmsgIdIPv6TClass")
     , (CmsgIdIPv4PktInfo, "CmsgIdIPv4PktInfo")
     , (CmsgIdIPv6PktInfo, "CmsgIdIPv6PktInfo")
-    , (CmsgIdFd, "CmsgIdFd")
+    , (CmsgIdFds, "CmsgIdFds")
     ]
 
 instance Show CmsgId where
diff --git a/network.cabal b/network.cabal
index 9c6de7c2..fc04ca68 100644
--- a/network.cabal
+++ b/network.cabal
@@ -207,3 +207,6 @@ test-suite spec
 
     if impl(ghc >=8)
         default-extensions: Strict StrictData
+
+    if os(windows)
+        cpp-options: -D_WIN32
diff --git a/tests/Network/SocketSpec.hs b/tests/Network/SocketSpec.hs
index 30294050..f2ac337f 100644
--- a/tests/Network/SocketSpec.hs
+++ b/tests/Network/SocketSpec.hs
@@ -379,9 +379,11 @@ spec = do
             let msgid = CmsgId (-300) (-300) in
             show msgid `shouldBe` "CmsgId (-300) (-300)"
 
+#if !defined(_WIN32)
     describe "bijective encodeCmsg-decodeCmsg roundtrip equality" $ do
         it "holds for [Fd]" $ forAll genFds $
             \x -> (decodeCmsg . encodeCmsg $ x) == Just (x :: [Fd])
+#endif
 
     describe "bijective read-show roundtrip equality" $ do
         it "holds for Family" $ forAll familyGen $