diff --git a/UPGRADING b/UPGRADING
index 5866bd3f..bb224c94 100644
--- a/UPGRADING
+++ b/UPGRADING
@@ -17,6 +17,7 @@ with newer versions.
 
   * socket API: according to the standard, SO_ERROR now only returns asynchronous errors.
     All other/normal/synchronous errors are (and always were) available via 'errno'.
+	LWIP_SOCKET_SET_ERRNO has been removed - 'errno' is always set - and required!
 
   * compatibility headers: moved from 'src/include/posix' to 'src/include/compat/posix',
     'src/include/compat/stdc' etc.
diff --git a/src/include/lwip/opt.h b/src/include/lwip/opt.h
index c361dcc0..4626a158 100644
--- a/src/include/lwip/opt.h
+++ b/src/include/lwip/opt.h
@@ -1849,13 +1849,6 @@
 #define LWIP_SOCKET                     1
 #endif
 
-/** LWIP_SOCKET_SET_ERRNO==1: Set errno when socket functions cannot complete
- * successfully, as required by POSIX. Default is POSIX-compliant.
- */
-#if !defined LWIP_SOCKET_SET_ERRNO || defined __DOXYGEN__
-#define LWIP_SOCKET_SET_ERRNO           1
-#endif
-
 /**
  * LWIP_COMPAT_SOCKETS==1: Enable BSD-style sockets functions names through defines.
  * LWIP_COMPAT_SOCKETS==2: Same as ==1 but correctly named functions are created.
diff --git a/src/include/lwip/priv/sockets_priv.h b/src/include/lwip/priv/sockets_priv.h
index 6a3a6980..d2ec9171 100644
--- a/src/include/lwip/priv/sockets_priv.h
+++ b/src/include/lwip/priv/sockets_priv.h
@@ -90,13 +90,9 @@ struct lwip_sock {
 #endif
 };
 
-#if LWIP_SOCKET_SET_ERRNO
 #ifndef set_errno
 #define set_errno(err) do { if (err) { errno = (err); } } while(0)
 #endif
-#else /* LWIP_SOCKET_SET_ERRNO */
-#define set_errno(err)
-#endif /* LWIP_SOCKET_SET_ERRNO */
 
 #if !LWIP_TCPIP_CORE_LOCKING
 /** Maximum optlen used by setsockopt/getsockopt */