diff --git a/gen/gen_code.cpp b/gen/gen_code.cpp
index c638752..ce7dff6 100644
--- a/gen/gen_code.cpp
+++ b/gen/gen_code.cpp
@@ -801,12 +801,13 @@ void put()
 			{ 0x0F, B10101110, 3, "stmxcsr" },
 			{ 0x0F, B10101110, 7, "clflush" }, // 0x80 is bug of nasm ?
 			{ 0xD9, NONE, 5, "fldcw" },
-			{ 0x9B, 0xD9, 7, "fstcw" },
+//			{ 0x9B, 0xD9, 7, "fstcw" }, // not correct order for fstcw [eax] on 64bit OS
 		};
 		for (int i = 0; i < NUM_OF_ARRAY(tbl); i++) {
 			const Tbl *p = &tbl[i];
 			printf("void %s(const Address& addr) { opModM(addr, Reg32(%d), 0x%02X, 0x%02X); }\n", p->name, p->ext, p->code1, p->code2);
 		}
+		printf("void fstcw(const Address& addr) { db(0x9B); opModM(addr, Reg32(7), 0xD9, NONE); }\n");
 	}
 	{
 		const struct Tbl {
diff --git a/sample/calc.cpp b/sample/calc.cpp
index 68e01a3..d93bc95 100644
--- a/sample/calc.cpp
+++ b/sample/calc.cpp
@@ -11,7 +11,7 @@
 #include <sstream>
 #include <map>
 #include "xbyak/xbyak.h"
-#ifdef _WIN32
+#ifdef _MSC_VER
 	#pragma warning(disable : 4127) // for boost(constant condition)
 	#pragma warning(disable : 4512) // for boost
 #endif
diff --git a/xbyak/xbyak.h b/xbyak/xbyak.h
index e309293..54400dd 100644
--- a/xbyak/xbyak.h
+++ b/xbyak/xbyak.h
@@ -28,7 +28,7 @@
 	#include <stdlib.h>
 #endif
 
-#ifdef __x86_64__
+#if defined(__x86_64__) && !defined(__MINGW64__)
 		#define XBYAK64_GCC
 #elif defined(_WIN64)
 		#define XBYAK64_WIN
diff --git a/xbyak/xbyak_mnemonic.h b/xbyak/xbyak_mnemonic.h
index 9df79ee..ca25225 100644
--- a/xbyak/xbyak_mnemonic.h
+++ b/xbyak/xbyak_mnemonic.h
@@ -489,7 +489,7 @@ void ldmxcsr(const Address& addr) { opModM(addr, Reg32(2), 0x0F, 0xAE); }
 void stmxcsr(const Address& addr) { opModM(addr, Reg32(3), 0x0F, 0xAE); }
 void clflush(const Address& addr) { opModM(addr, Reg32(7), 0x0F, 0xAE); }
 void fldcw(const Address& addr) { opModM(addr, Reg32(5), 0xD9, 0x100); }
-void fstcw(const Address& addr) { opModM(addr, Reg32(7), 0x9B, 0xD9); }
+void fstcw(const Address& addr) { db(0x9B); opModM(addr, Reg32(7), 0xD9, NONE); }
 void movntpd(const Address& addr, const Xmm& reg) { opModM(addr, Reg16(reg.getIdx()), 0x0F, 0x2B); }
 void movntdq(const Address& addr, const Xmm& reg) { opModM(addr, Reg16(reg.getIdx()), 0x0F, 0xE7); }
 void movsx(const Reg& reg, const Operand& op) { opMovxx(reg, op, 0xBE); }