diff --git a/readme.md b/readme.md
index 15d8bef..44489d0 100644
--- a/readme.md
+++ b/readme.md
@@ -403,6 +403,10 @@ This library contains some part of the followings software licensed by BSD-3-Cla
 * [_Skew Frobenius Map and Efficient Scalar Multiplication for Pairing–Based Cryptography_](https://www.researchgate.net/publication/221282560_Skew_Frobenius_Map_and_Efficient_Scalar_Multiplication_for_Pairing-Based_Cryptography),
 Y. Sakemi, Y. Nogami, K. Okeya, Y. Morikawa, CANS 2008.
 
+# History
+
+* 2019/Jan/31 fix crash on x64-CPU without AVX
+
 # Author
 
 光成滋生 MITSUNARI Shigeo(herumi@nifty.com)
diff --git a/src/fp.cpp b/src/fp.cpp
index 41e98e4..ebd9477 100644
--- a/src/fp.cpp
+++ b/src/fp.cpp
@@ -318,9 +318,9 @@ static bool initForMont(Op& op, const Unit *p, Mode mode)
 	if (mode != FP_XBYAK) return true;
 #ifdef MCL_USE_XBYAK
 	if (op.fg == 0) op.fg = Op::createFpGenerator();
-	op.fg->init(op);
+	bool useXbyak = op.fg->init(op);
 
-	if (op.isMont && N <= 4) {
+	if (useXbyak && op.isMont && N <= 4) {
 		op.fp_invOp = &invOpForMontC;
 		initInvTbl(op);
 	}
diff --git a/src/fp_generator.hpp b/src/fp_generator.hpp
index a018c03..b496bc4 100644
--- a/src/fp_generator.hpp
+++ b/src/fp_generator.hpp
@@ -307,19 +307,20 @@ struct FpGenerator : Xbyak::CodeGenerator {
 		useMulx_ = cpu_.has(Xbyak::util::Cpu::tBMI2);
 		useAdx_ = cpu_.has(Xbyak::util::Cpu::tADX);
 	}
-	void init(Op& op)
+	bool init(Op& op)
 	{
+		if (!cpu_.has(Xbyak::util::Cpu::tAVX)) return false;
 		reset(); // reset jit code for reuse
 		setProtectModeRW(); // read/write memory
 		init_inner(op);
 //		printf("code size=%d\n", (int)getSize());
 		setProtectModeRE(); // set read/exec memory
+		return true;
 	}
 private:
 	void init_inner(Op& op)
 	{
 		op_ = &op;
-		if (!cpu_.has(Xbyak::util::Cpu::tAVX)) return;
 		L(pL_);
 		p_ = reinterpret_cast<const uint64_t*>(getCurr());
 		for (size_t i = 0; i < op.N; i++) {