diff --git a/src/oatpp/core/IODefinitions.hpp b/src/oatpp/core/IODefinitions.hpp
index dfb62f5d..26ca9c03 100644
--- a/src/oatpp/core/IODefinitions.hpp
+++ b/src/oatpp/core/IODefinitions.hpp
@@ -28,6 +28,10 @@
 #include "oatpp/core/async/Error.hpp"
 #include "oatpp/core/Types.hpp"
 
+#if !defined(WIN32) && !defined(_WIN32)
+#include <sys/socket.h>
+#endif
+
 namespace oatpp {
 
 /**
@@ -39,9 +43,11 @@ namespace oatpp {
   #else
     typedef unsigned long v_io_handle;
   #endif
+    typedef int v_sock_size;
     constexpr const v_io_handle INVALID_IO_HANDLE = v_io_handle (-1);
 #else
   typedef int v_io_handle;
+  typedef socklen_t v_sock_size;
   constexpr const v_io_handle INVALID_IO_HANDLE = (-1);
 #endif
 
diff --git a/src/oatpp/network/tcp/client/ConnectionProvider.cpp b/src/oatpp/network/tcp/client/ConnectionProvider.cpp
index d84ba7d3..ffef432c 100644
--- a/src/oatpp/network/tcp/client/ConnectionProvider.cpp
+++ b/src/oatpp/network/tcp/client/ConnectionProvider.cpp
@@ -123,7 +123,7 @@ provider::ResourceHandle<data::stream::IOStream> ConnectionProvider::get() {
 
     if(clientHandle >= 0) {
 
-      if(connect(clientHandle, currResult->ai_addr, static_cast<socklen_t>(currResult->ai_addrlen)) == 0) {
+      if(connect(clientHandle, currResult->ai_addr, static_cast<v_sock_size>(currResult->ai_addrlen)) == 0) {
         break;
       } else {
           err = errno;
@@ -282,7 +282,7 @@ oatpp::async::CoroutineStarterForResult<const provider::ResourceHandle<data::str
     Action doConnect() {
       errno = 0;
 
-      auto res = connect(m_clientHandle, m_currentResult->ai_addr, static_cast<socklen_t>(m_currentResult->ai_addrlen));
+      auto res = connect(m_clientHandle, m_currentResult->ai_addr, static_cast<v_sock_size>(m_currentResult->ai_addrlen));
 
 #if defined(WIN32) || defined(_WIN32)
 
diff --git a/src/oatpp/network/tcp/server/ConnectionProvider.cpp b/src/oatpp/network/tcp/server/ConnectionProvider.cpp
index 48f1f888..5b498081 100644
--- a/src/oatpp/network/tcp/server/ConnectionProvider.cpp
+++ b/src/oatpp/network/tcp/server/ConnectionProvider.cpp
@@ -46,7 +46,7 @@
 
 // Workaround for MinGW from: https://www.mail-archive.com/users@ipv6.org/msg02107.html
 #if defined(__MINGW32__) && _WIN32_WINNT < 0x0600
-  const char * inet_ntop (int af, const void *src, char *dst, socklen_t cnt) {
+  const char * inet_ntop (int af, const void *src, char *dst, oatpp::v_sock_size cnt) {
     if (af == AF_INET) {
       struct sockaddr_in in;
 
@@ -228,7 +228,7 @@ oatpp::v_io_handle ConnectionProvider::instantiateServer(){
   // Update port after binding (typicaly in case of port = 0)
   struct ::sockaddr_in s_in;
   ::memset(&s_in, 0, sizeof(s_in));
-  ::socklen_t s_in_len = sizeof(s_in);
+  oatpp::v_sock_size s_in_len = sizeof(s_in);
   ::getsockname(serverHandle, (struct sockaddr *)&s_in, &s_in_len);
   setProperty(PROPERTY_PORT, oatpp::utils::conversion::int32ToStr(ntohs(s_in.sin_port)));
 
@@ -280,7 +280,7 @@ oatpp::v_io_handle ConnectionProvider::instantiateServer(){
                    "Warning. Failed to set %s for accepting socket: %s", "SO_REUSEADDR", strerror(errno))
       }
 
-      if (bind(serverHandle, currResult->ai_addr, static_cast<socklen_t>(currResult->ai_addrlen)) == 0 &&
+      if (bind(serverHandle, currResult->ai_addr, static_cast<v_sock_size>(currResult->ai_addrlen)) == 0 &&
           listen(serverHandle, 10000) == 0)
       {
         break;
@@ -309,7 +309,7 @@ oatpp::v_io_handle ConnectionProvider::instantiateServer(){
   // Update port after binding (typicaly in case of port = 0)
   ::sockaddr_in s_in;
   ::memset(&s_in, 0, sizeof(s_in));
-  ::socklen_t s_in_len = sizeof(s_in);
+  oatpp::v_sock_size s_in_len = sizeof(s_in);//FIXME trace
   ::getsockname(serverHandle, reinterpret_cast<sockaddr*>(&s_in), &s_in_len);
   setProperty(PROPERTY_PORT, oatpp::utils::conversion::int32ToStr(ntohs(s_in.sin_port)));
 
@@ -351,7 +351,7 @@ provider::ResourceHandle<data::stream::IOStream> ConnectionProvider::getDefaultC
 provider::ResourceHandle<data::stream::IOStream> ConnectionProvider::getExtendedConnection() {
 
   sockaddr_storage clientAddress;
-  socklen_t clientAddressSize = sizeof(clientAddress);
+  v_sock_size clientAddressSize = sizeof(clientAddress);
 
   data::stream::Context::Properties properties;
 
diff --git a/src/oatpp/parser/json/mapping/Deserializer.cpp b/src/oatpp/parser/json/mapping/Deserializer.cpp
index 4c44fe6e..180625c3 100644
--- a/src/oatpp/parser/json/mapping/Deserializer.cpp
+++ b/src/oatpp/parser/json/mapping/Deserializer.cpp
@@ -494,7 +494,7 @@ oatpp::Void Deserializer::deserializeObject(Deserializer* deserializer, parser::
 }
 
 oatpp::Void Deserializer::deserialize(parser::Caret& caret, const Type* const type) {
-  v_uint32 id = static_cast<v_uint32>(type->classId.id);
+  auto id = static_cast<v_uint32>(type->classId.id);
   auto& method = m_methods[id];
   if(method) {
     return (*method)(this, caret, type);
diff --git a/src/oatpp/parser/json/mapping/Serializer.cpp b/src/oatpp/parser/json/mapping/Serializer.cpp
index a4e638af..c0df709c 100644
--- a/src/oatpp/parser/json/mapping/Serializer.cpp
+++ b/src/oatpp/parser/json/mapping/Serializer.cpp
@@ -259,7 +259,7 @@ void Serializer::serializeObject(Serializer* serializer,
 void Serializer::serialize(data::stream::ConsistentOutputStream* stream,
                            const oatpp::Void& polymorph)
 {
-  v_uint32 id = static_cast<v_uint32>(polymorph.getValueType()->classId.id);
+  auto id = static_cast<v_uint32>(polymorph.getValueType()->classId.id);
   auto& method = m_methods[id];
   if(method) {
     (*method)(this, stream, polymorph);