Index: libcxx/test/support/platform_support.h
===================================================================
--- libcxx/test/support/platform_support.h
+++ libcxx/test/support/platform_support.h
@@ -57,7 +57,9 @@
 #include <locale>
 #include <string>
 #if defined(_WIN32) || defined(__MINGW32__)
+#   define WIN32_LEAN_AND_MEAN // Reduce overhead of including windows.h
 #   include <io.h> // _mktemp_s
+#   include <windows.h> // MAX_PATH, GetTempPath, GetTempFileName
 #else
 #   include <unistd.h> // close
 #endif