diff --git a/Network/Socket/Types.hsc b/Network/Socket/Types.hsc
index 13fe3a8d..fd4d8c7b 100644
--- a/Network/Socket/Types.hsc
+++ b/Network/Socket/Types.hsc
@@ -1156,15 +1156,16 @@ unixPathMax = #const sizeof(((struct sockaddr_un *)NULL)->sun_path)
 -- | Write the given 'SockAddr' to the given memory location.
 pokeSockAddr :: Ptr a -> SockAddr -> IO ()
 pokeSockAddr p sa@(SockAddrUnix path) = do
-    when (length path > unixPathMax) $ error
+    let pathC = map castCharToCChar path
+        len = length pathC
+    when (len >= unixPathMax) $ error
       $ "pokeSockAddr: path is too long in SockAddrUnix " <> show path
-      <> ", length " <> show (length path) <> ", unixPathMax " <> show unixPathMax
+      <> ", length " <> show len <> ", unixPathMax " <> show unixPathMax
     zeroMemory p $ fromIntegral $ sizeOfSockAddr sa
 # if defined(HAVE_STRUCT_SOCKADDR_SA_LEN)
     (#poke struct sockaddr_un, sun_len) p ((#const sizeof(struct sockaddr_un)) :: Word8)
 # endif
     (#poke struct sockaddr_un, sun_family) p ((#const AF_UNIX) :: CSaFamily)
-    let pathC = map castCharToCChar path
     -- the buffer is already filled with nulls.
     pokeArray ((#ptr struct sockaddr_un, sun_path) p) pathC
 pokeSockAddr p (SockAddrInet port addr) = do