Index: include/__config
===================================================================
--- include/__config
+++ include/__config
@@ -21,7 +21,6 @@
 
 #if !_WIN32
 #include <unistd.h>
-#include <errno.h>  // for ELAST on FreeBSD
 #endif
 
 #define _LIBCPP_VERSION 1101
@@ -643,21 +642,6 @@
 #define _LIBCPP_WCTYPE_IS_MASK
 #endif
 
-#if defined(ELAST)
-#define _LIBCPP_ELAST ELAST
-#elif defined(__linux__)
-#define _LIBCPP_ELAST 4095
-#elif defined(_NEWLIB_VERSION)
-#define _LIBCPP_ELAST __ELASTERROR
-#elif defined(__APPLE__)
-// Not _LIBCPP_ELAST needed on Apple
-#elif defined(__sun__)
-#define _LIBCPP_ELAST ESTALE
-#else
-// Warn here so that the person doing the libcxx port has an easier time:
-#warning This platform's ELAST hasn't been ported yet
-#endif
-
 #ifndef _LIBCPP_TRIVIAL_PAIR_COPY_CTOR
 #  define _LIBCPP_TRIVIAL_PAIR_COPY_CTOR 1
 #endif
Index: src/config_elast.h
===================================================================
--- /dev/null
+++ src/config_elast.h
@@ -0,0 +1,36 @@
+//===----------------------- config_elast.h -------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_CONFIG_ELAST
+#define _LIBCPP_CONFIG_ELAST
+
+#if defined(_WIN32)
+#include <stdlib.h>
+#else
+#include <errno.h>
+#endif
+
+#if defined(ELAST)
+#define _LIBCPP_ELAST ELAST
+#elif defined(_NEWLIB_VERSION)
+#define _LIBCPP_ELAST __ELASTERROR
+#elif defined(__linux__)
+#define _LIBCPP_ELAST 4095
+#elif defined(__APPLE__)
+// No _LIBCPP_ELAST needed on Apple
+#elif defined(__sun__)
+#define _LIBCPP_ELAST ESTALE
+#elif defined(_WIN32)
+#define _LIBCPP_ELAST _sys_nerr
+#else
+// Warn here so that the person doing the libcxx port has an easier time:
+#warning This platform's ELAST hasn't been ported yet
+#endif
+
+#endif // _LIBCPP_CONFIG_ELAST
Index: src/ios.cpp
===================================================================
--- src/ios.cpp
+++ src/ios.cpp
@@ -8,16 +8,20 @@
 //===----------------------------------------------------------------------===//
 
 #include "__config"
+
 #include "ios"
-#include "streambuf"
-#include "istream"
-#include "string"
+
+#include <stdlib.h>
+
 #include "__locale"
 #include "algorithm"
+#include "config_elast.h"
+#include "istream"
+#include "limits"
 #include "memory"
 #include "new"
-#include "limits"
-#include <stdlib.h>
+#include "streambuf"
+#include "string"
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
Index: src/system_error.cpp
===================================================================
--- src/system_error.cpp
+++ src/system_error.cpp
@@ -7,11 +7,14 @@
 //
 //===----------------------------------------------------------------------===//
 
-#define _LIBCPP_BUILDING_SYSTEM_ERROR
 #include "__config"
+
+#define _LIBCPP_BUILDING_SYSTEM_ERROR
 #include "system_error"
-#include "string"
+
+#include "config_elast.h"
 #include "cstring"
+#include "string"
 
 _LIBCPP_BEGIN_NAMESPACE_STD