diff --git a/Network/Wai/Logger/Apache.hs b/Network/Wai/Logger/Apache.hs
--- a/Network/Wai/Logger/Apache.hs
+++ b/Network/Wai/Logger/Apache.hs
@@ -123,11 +123,11 @@
 -- >>> getSourceFromHeader defaultRequest { requestHeaders = [ ("X-Forwarded-For", "127.0.0.1") ] }
 -- "127.0.0.1"
 -- >>> getSourceFromHeader defaultRequest { requestHeaders = [ ("Something", "127.0.0.1") ] }
--- ""
+-- "-"
 -- >>> getSourceFromHeader defaultRequest { requestHeaders = [] }
--- ""
+-- "-"
 getSourceFromHeader :: Request -> ByteString
-getSourceFromHeader = fromMaybe "" . getSource
+getSourceFromHeader = fromMaybe "-" . getSource
 
 -- |
 -- >>> getSourceFromFallback defaultRequest { requestHeaders = [ ("X-Real-IP", "127.0.0.1") ] }
diff --git a/Network/Wai/Logger/IP.hs b/Network/Wai/Logger/IP.hs
--- a/Network/Wai/Logger/IP.hs
+++ b/Network/Wai/Logger/IP.hs
@@ -46,4 +46,4 @@
 showSockAddr (SockAddrInet6 _ _ (0,0,0x0000ffff,addr4) _) = showIPv4 addr4 False
 showSockAddr (SockAddrInet6 _ _ (0,0,0,1) _)              = "::1"
 showSockAddr (SockAddrInet6 _ _ addr6 _)                  = showIPv6 addr6
-showSockAddr _                                            = "unknownSocket"
+showSockAddr (SockAddrUnix _)                             = "-"
diff --git a/wai-logger.cabal b/wai-logger.cabal
--- a/wai-logger.cabal
+++ b/wai-logger.cabal
@@ -1,5 +1,5 @@
 Name:                   wai-logger
-Version:                2.3.7
+Version:                2.4.0
 Author:                 Kazu Yamamoto <kazu@iij.ad.jp>
 Maintainer:             Kazu Yamamoto <kazu@iij.ad.jp>
 License:                BSD3