diff --git a/Network/Wai/Handler/Warp.hs b/Network/Wai/Handler/Warp.hs
--- a/Network/Wai/Handler/Warp.hs
+++ b/Network/Wai/Handler/Warp.hs
@@ -338,7 +338,7 @@
 setHTTP2Disabled :: Settings -> Settings
 setHTTP2Disabled y = y { settingsHTTP2Enabled = False }
 
--- | Setting a log function.
+-- | Setting a log function. `Integer` is the body length of a response.
 --
 -- Since 3.X.X
 setLogger :: (Request -> H.Status -> Maybe Integer -> IO ())
diff --git a/Network/Wai/Handler/Warp/Run.hs b/Network/Wai/Handler/Warp/Run.hs
--- a/Network/Wai/Handler/Warp/Run.hs
+++ b/Network/Wai/Handler/Warp/Run.hs
@@ -130,7 +130,8 @@
         (s, sa) <- accept socket
 #endif
         setSocketCloseOnExec s
-        setSocketOption s NoDelay 1
+        -- NoDelay causes an error for AF_UNIX.
+        setSocketOption s NoDelay 1 `E.catch` \(E.SomeException _) -> return ()
         conn <- socketConnection s
         return (conn, sa)
 
diff --git a/warp.cabal b/warp.cabal
--- a/warp.cabal
+++ b/warp.cabal
@@ -1,5 +1,5 @@
 Name:                warp
-Version:             3.2.4
+Version:             3.2.5
 Synopsis:            A fast, light-weight web server for WAI applications.
 License:             MIT
 License-file:        LICENSE