diff --git a/include/basetsd.h b/include/basetsd.h
index 8f853a41e8d..409f95816f6 100644
--- a/include/basetsd.h
+++ b/include/basetsd.h
@@ -59,7 +59,7 @@ extern "C" {
 #    define __int32 int
 #  endif
 #  ifndef __int64
-#    ifdef _WIN64
+#    if defined(_WIN64) && !defined(__MINGW64__)
 #      define __int64 long
 #    else
 #      define __int64 long long
diff --git a/include/msvcrt/direct.h b/include/msvcrt/direct.h
index b0c4af816ca..d71aee0b632 100644
--- a/include/msvcrt/direct.h
+++ b/include/msvcrt/direct.h
@@ -29,7 +29,7 @@ typedef unsigned short wchar_t;
 #endif
 
 #if !defined(_MSC_VER) && !defined(__int64)
-# ifdef _WIN64
+# if defined(_WIN64) && !defined(__MINGW64__)
 #   define __int64 long
 # else
 #   define __int64 long long
diff --git a/include/msvcrt/io.h b/include/msvcrt/io.h
index 6009fe9d8a9..ef4a312d271 100644
--- a/include/msvcrt/io.h
+++ b/include/msvcrt/io.h
@@ -25,7 +25,7 @@ typedef unsigned short wchar_t;
 #endif
 
 #if !defined(_MSC_VER) && !defined(__int64)
-# ifdef _WIN64
+# if defined(_WIN64) && !defined(__MINGW64__)
 #   define __int64 long
 # else
 #   define __int64 long long
diff --git a/include/msvcrt/malloc.h b/include/msvcrt/malloc.h
index bee2173eb69..b71c4fd2b80 100644
--- a/include/msvcrt/malloc.h
+++ b/include/msvcrt/malloc.h
@@ -39,7 +39,7 @@
 #endif
 
 #if !defined(_MSC_VER) && !defined(__int64)
-# ifdef _WIN64
+# if defined(_WIN64) && !defined(__MINGW64__)
 #   define __int64 long
 # else
 #   define __int64 long long
diff --git a/include/msvcrt/mbstring.h b/include/msvcrt/mbstring.h
index 124d215c0b0..a9c38cf4f51 100644
--- a/include/msvcrt/mbstring.h
+++ b/include/msvcrt/mbstring.h
@@ -30,7 +30,7 @@
 #endif
 
 #if !defined(_MSC_VER) && !defined(__int64)
-# ifdef _WIN64
+# if defined(_WIN64) && !defined(__MINGW64__)
 #   define __int64 long
 # else
 #   define __int64 long long
diff --git a/include/msvcrt/memory.h b/include/msvcrt/memory.h
index a5217df85ea..e2f5a37bdda 100644
--- a/include/msvcrt/memory.h
+++ b/include/msvcrt/memory.h
@@ -16,7 +16,7 @@
 #endif
 
 #if !defined(_MSC_VER) && !defined(__int64)
-# ifdef _WIN64
+# if defined(_WIN64) && !defined(__MINGW64__)
 #   define __int64 long
 # else
 #   define __int64 long long
diff --git a/include/msvcrt/search.h b/include/msvcrt/search.h
index af648d58ac7..ff5bf80a559 100644
--- a/include/msvcrt/search.h
+++ b/include/msvcrt/search.h
@@ -28,7 +28,7 @@
 #endif
 
 #if !defined(_MSC_VER) && !defined(__int64)
-# ifdef _WIN64
+# if defined(_WIN64) && !defined(__MINGW64__)
 #   define __int64 long
 # else
 #   define __int64 long long
diff --git a/include/msvcrt/stddef.h b/include/msvcrt/stddef.h
index eb45c87da7d..d0fe7de3ef2 100644
--- a/include/msvcrt/stddef.h
+++ b/include/msvcrt/stddef.h
@@ -28,7 +28,7 @@
 #endif
 
 #if !defined(_MSC_VER) && !defined(__int64)
-# ifdef _WIN64
+# if defined(_WIN64) && !defined(__MINGW64__)
 #   define __int64 long
 # else
 #   define __int64 long long
diff --git a/include/msvcrt/stdio.h b/include/msvcrt/stdio.h
index b1776646211..55d944419d1 100644
--- a/include/msvcrt/stdio.h
+++ b/include/msvcrt/stdio.h
@@ -22,7 +22,7 @@
 #endif
 
 #if !defined(_MSC_VER) && !defined(__int64)
-# ifdef _WIN64
+# if defined(_WIN64) && !defined(__MINGW64__)
 #   define __int64 long
 # else
 #   define __int64 long long
diff --git a/include/msvcrt/stdlib.h b/include/msvcrt/stdlib.h
index ddaae617f50..0010c3310fe 100644
--- a/include/msvcrt/stdlib.h
+++ b/include/msvcrt/stdlib.h
@@ -49,7 +49,7 @@ typedef struct
 #endif
 
 #if !defined(_MSC_VER) && !defined(__int64)
-# ifdef _WIN64
+# if defined(_WIN64) && !defined(__MINGW64__)
 #   define __int64 long
 # else
 #   define __int64 long long
diff --git a/include/msvcrt/string.h b/include/msvcrt/string.h
index a963553312b..d70cd23947e 100644
--- a/include/msvcrt/string.h
+++ b/include/msvcrt/string.h
@@ -23,7 +23,7 @@ typedef unsigned short wchar_t;
 #endif
 
 #if !defined(_MSC_VER) && !defined(__int64)
-# ifdef _WIN64
+# if defined(_WIN64) && !defined(__MINGW64__)
 #   define __int64 long
 # else
 #   define __int64 long long
diff --git a/include/msvcrt/sys/types.h b/include/msvcrt/sys/types.h
index 663ad629b66..dac8d64c984 100644
--- a/include/msvcrt/sys/types.h
+++ b/include/msvcrt/sys/types.h
@@ -28,7 +28,7 @@
 #endif
 
 #if !defined(_MSC_VER) && !defined(__int64)
-# ifdef _WIN64
+# if defined(_WIN64) && !defined(__MINGW64__)
 #   define __int64 long
 # else
 #   define __int64 long long
diff --git a/include/msvcrt/time.h b/include/msvcrt/time.h
index deb17e1439d..9b9a5164f30 100644
--- a/include/msvcrt/time.h
+++ b/include/msvcrt/time.h
@@ -37,7 +37,7 @@ typedef unsigned short wchar_t;
 #endif
 
 #if !defined(_MSC_VER) && !defined(__int64)
-# ifdef _WIN64
+# if defined(_WIN64) && !defined(__MINGW64__)
 #   define __int64 long
 # else
 #   define __int64 long long
diff --git a/include/msvcrt/wchar.h b/include/msvcrt/wchar.h
index 611b738d832..4e4892ff1a7 100644
--- a/include/msvcrt/wchar.h
+++ b/include/msvcrt/wchar.h
@@ -42,7 +42,7 @@ typedef unsigned short wchar_t;
 #endif
 
 #if !defined(_MSC_VER) && !defined(__int64)
-# ifdef _WIN64
+# if defined(_WIN64) && !defined(__MINGW64__)
 #   define __int64 long
 # else
 #   define __int64 long long
diff --git a/include/windef.h b/include/windef.h
index 8c0a0bb3eab..3c9de7a9137 100644
--- a/include/windef.h
+++ b/include/windef.h
@@ -37,18 +37,19 @@ extern "C" {
 
 /* Calling conventions definitions */
 
-#if defined(__i386__) && !defined(_X86_)
-# define _X86_
-#endif
-
-#if defined(_X86_) && !defined(__i386__)
-# define __i386__
-#endif
-
 #if defined(__x86_64__) && !defined(_WIN64)
 #define _WIN64
 #endif
 
+#ifndef _WIN64
+# if defined(__i386__) && !defined(_X86_)
+#  define _X86_
+# endif
+# if defined(_X86_) && !defined(__i386__)
+#  define __i386__
+# endif
+#endif
+
 #ifndef __stdcall
 # ifdef __i386__
 #  ifdef __GNUC__