diff --git a/lib/Support/CrashRecoveryContext.cpp b/lib/Support/CrashRecoveryContext.cpp
index 92c370dda44..29f73fc539c 100644
--- a/lib/Support/CrashRecoveryContext.cpp
+++ b/lib/Support/CrashRecoveryContext.cpp
@@ -132,7 +132,7 @@ CrashRecoveryContext::unregisterCleanup(CrashRecoveryContextCleanup *cleanup) {
 
 #ifdef LLVM_ON_WIN32
 
-#include "Windows/Windows.h"
+#include "Windows/WindowsSupport.h"
 
 // On Windows, we can make use of vectored exception handling to
 // catch most crashing situations.  Note that this does mean
diff --git a/lib/Support/Threading.cpp b/lib/Support/Threading.cpp
index 13fba2ea258..9d7ac6c18de 100644
--- a/lib/Support/Threading.cpp
+++ b/lib/Support/Threading.cpp
@@ -103,7 +103,7 @@ void llvm::llvm_execute_on_thread(void (*Fn)(void*), void *UserData,
   ::pthread_attr_destroy(&Attr);
 }
 #elif LLVM_ENABLE_THREADS!=0 && defined(LLVM_ON_WIN32)
-#include "Windows/Windows.h"
+#include "Windows/WindowsSupport.h"
 #include <process.h>
 
 struct ThreadInfo {
diff --git a/lib/Support/Windows/DynamicLibrary.inc b/lib/Support/Windows/DynamicLibrary.inc
index 5a7b21920a9..504471eaff3 100644
--- a/lib/Support/Windows/DynamicLibrary.inc
+++ b/lib/Support/Windows/DynamicLibrary.inc
@@ -11,7 +11,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "Windows.h"
+#include "WindowsSupport.h"
 
 #ifdef __MINGW32__
  #include <imagehlp.h>
diff --git a/lib/Support/Windows/Host.inc b/lib/Support/Windows/Host.inc
index 2e6d6f19037..7bda89dc49c 100644
--- a/lib/Support/Windows/Host.inc
+++ b/lib/Support/Windows/Host.inc
@@ -11,7 +11,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "Windows.h"
+#include "WindowsSupport.h"
 #include <cstdio>
 #include <string>
 
diff --git a/lib/Support/Windows/Memory.inc b/lib/Support/Windows/Memory.inc
index 12604524d40..ebe78782b90 100644
--- a/lib/Support/Windows/Memory.inc
+++ b/lib/Support/Windows/Memory.inc
@@ -17,7 +17,7 @@
 #include "llvm/Support/Process.h"
 
 // The Windows.h header must be the last one included.
-#include "Windows.h"
+#include "WindowsSupport.h"
 
 namespace {
 
diff --git a/lib/Support/Windows/Mutex.inc b/lib/Support/Windows/Mutex.inc
index 583dc6359a1..ab79d079122 100644
--- a/lib/Support/Windows/Mutex.inc
+++ b/lib/Support/Windows/Mutex.inc
@@ -16,7 +16,7 @@
 //===          is guaranteed to work on *all* Win32 variants.
 //===----------------------------------------------------------------------===//
 
-#include "Windows.h"
+#include "WindowsSupport.h"
 #include "llvm/Support/Mutex.h"
 
 namespace llvm {
diff --git a/lib/Support/Windows/Path.inc b/lib/Support/Windows/Path.inc
index 8329d271b39..46e9ce7acb2 100644
--- a/lib/Support/Windows/Path.inc
+++ b/lib/Support/Windows/Path.inc
@@ -24,7 +24,7 @@
 
 // These two headers must be included last, and make sure shlobj is required
 // after Windows.h to make sure it picks up our definition of _WIN32_WINNT
-#include "Windows.h"
+#include "WindowsSupport.h"
 #include <shlobj.h>
 
 #undef max
diff --git a/lib/Support/Windows/Process.inc b/lib/Support/Windows/Process.inc
index a0e3bc413a3..a794ca08f67 100644
--- a/lib/Support/Windows/Process.inc
+++ b/lib/Support/Windows/Process.inc
@@ -15,7 +15,7 @@
 #include <malloc.h>
 
 // The Windows.h header must be after LLVM and standard headers.
-#include "Windows.h"
+#include "WindowsSupport.h"
 
 #include <direct.h>
 #include <io.h>
diff --git a/lib/Support/Windows/Program.inc b/lib/Support/Windows/Program.inc
index dc09738e2e7..365e87eea59 100644
--- a/lib/Support/Windows/Program.inc
+++ b/lib/Support/Windows/Program.inc
@@ -11,7 +11,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "Windows.h"
+#include "WindowsSupport.h"
 #include "llvm/ADT/OwningPtr.h"
 #include "llvm/Support/FileSystem.h"
 #include <cstdio>
diff --git a/lib/Support/Windows/RWMutex.inc b/lib/Support/Windows/RWMutex.inc
index c4318448e7c..00d0e93d8d5 100644
--- a/lib/Support/Windows/RWMutex.inc
+++ b/lib/Support/Windows/RWMutex.inc
@@ -16,7 +16,7 @@
 //===          is guaranteed to work on *all* Win32 variants.
 //===----------------------------------------------------------------------===//
 
-#include "Windows.h"
+#include "WindowsSupport.h"
 
 namespace llvm {
 using namespace sys;
diff --git a/lib/Support/Windows/Signals.inc b/lib/Support/Windows/Signals.inc
index 5add76a0c03..a28b0b8003d 100644
--- a/lib/Support/Windows/Signals.inc
+++ b/lib/Support/Windows/Signals.inc
@@ -17,7 +17,7 @@
 #include <vector>
 
 // The Windows.h header must be after LLVM and standard headers.
-#include "Windows.h"
+#include "WindowsSupport.h"
 
 #ifdef __MINGW32__
  #include <imagehlp.h>
diff --git a/lib/Support/Windows/ThreadLocal.inc b/lib/Support/Windows/ThreadLocal.inc
index 057deb325d6..3914cf72fa9 100644
--- a/lib/Support/Windows/ThreadLocal.inc
+++ b/lib/Support/Windows/ThreadLocal.inc
@@ -16,7 +16,7 @@
 //===          is guaranteed to work on *all* Win32 variants.
 //===----------------------------------------------------------------------===//
 
-#include "Windows.h"
+#include "WindowsSupport.h"
 #include "llvm/Support/ThreadLocal.h"
 
 namespace llvm {
diff --git a/lib/Support/Windows/TimeValue.inc b/lib/Support/Windows/TimeValue.inc
index 98b07d6e447..6c59024d9c6 100644
--- a/lib/Support/Windows/TimeValue.inc
+++ b/lib/Support/Windows/TimeValue.inc
@@ -11,7 +11,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "Windows.h"
+#include "WindowsSupport.h"
 #include <cctype>
 #include <time.h>
 
diff --git a/lib/Support/Windows/Windows.h b/lib/Support/Windows/WindowsSupport.h
similarity index 92%
rename from lib/Support/Windows/Windows.h
rename to lib/Support/Windows/WindowsSupport.h
index 5666de267d7..6bef4444602 100644
--- a/lib/Support/Windows/Windows.h
+++ b/lib/Support/Windows/WindowsSupport.h
@@ -1,4 +1,4 @@
-//===- Win32/Win32.h - Common Win32 Include File ----------------*- C++ -*-===//
+//===- WindowsSupport.h - Common Windows Include File -----------*- C++ -*-===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -7,7 +7,10 @@
 //
 //===----------------------------------------------------------------------===//
 //
-// This file defines things specific to Win32 implementations.
+// This file defines things specific to Windows implementations.  In addition to
+// providing some helpers for working with win32 APIs, this header wraps
+// <windows.h> with some portability macros.  Always include WindowsSupport.h
+// instead of including <windows.h> directly.
 //
 //===----------------------------------------------------------------------===//