diff --git a/include/mcl/fp_generator.hpp b/include/mcl/fp_generator.hpp
index 04457b3..559e253 100644
--- a/include/mcl/fp_generator.hpp
+++ b/include/mcl/fp_generator.hpp
@@ -195,7 +195,7 @@ struct FpGenerator : Xbyak::CodeGenerator {
 		@param p [in] pointer to prime
 		@param pn [in] length of prime
 	*/
-	void init(Op& /*op*/, const uint64_t *p, int pn)
+	void init(Op& op, const uint64_t *p, int pn)
 	{
 		if (pn < 2) throw cybozu::Exception("mcl:FpGenerator:small pn") << pn;
 		p_ = p;
@@ -239,6 +239,21 @@ struct FpGenerator : Xbyak::CodeGenerator {
 		gen_shr1();
 		preInv_ = getCurr<int2op>();
 		gen_preInv();
+
+		op.fp_neg = Xbyak::CastTo<void2u>(neg_);
+		op.fp_add = Xbyak::CastTo<void3u>(add_);
+		op.fp_sub = Xbyak::CastTo<void3u>(sub_);
+		op.fp_addNC = Xbyak::CastTo<void3u>(addNC_);
+		op.fp_subNC = Xbyak::CastTo<void3u>(subNC_);
+		op.fp_mul = Xbyak::CastTo<void3u>(mul_);
+		op.fp_sqr = Xbyak::CastTo<void2u>(sqr_);
+
+		if (pn <= 4) {
+			if (montRed_) {
+				op.fp_mod = Xbyak::CastTo<void2u>(montRed_);
+			}
+			op.fp_preInv = Xbyak::CastTo<int2u>(preInv_);
+		}
 	}
 	void gen_addSubNC(bool isAdd)
 	{
diff --git a/src/fp.cpp b/src/fp.cpp
index 49e8e36..f3b1ef6 100644
--- a/src/fp.cpp
+++ b/src/fp.cpp
@@ -365,22 +365,10 @@ static void initForMont(Op& op, const Unit *p, Mode mode)
 	if (fg == 0) return;
 	fg->init(op, p, (int)N);
 
-	op.fp_neg = Xbyak::CastTo<void2u>(fg->neg_);
-	op.fp_add = Xbyak::CastTo<void3u>(fg->add_);
-	op.fp_sub = Xbyak::CastTo<void3u>(fg->sub_);
-	op.fp_addNC = Xbyak::CastTo<void3u>(fg->addNC_);
-	op.fp_subNC = Xbyak::CastTo<void3u>(fg->subNC_);
-	op.fp_mul = Xbyak::CastTo<void3u>(fg->mul_);
-	op.fp_sqr = Xbyak::CastTo<void2u>(fg->sqr_);
 	if (N <= 4) {
-		if (fg->montRed_) {
-			op.fp_mod = Xbyak::CastTo<void2u>(fg->montRed_);
-		}
-		op.fp_preInv = Xbyak::CastTo<int2u>(op.fg->preInv_);
 		op.fp_invOp = &invOpForMontC;
 		initInvTbl(op);
 	}
-
 #endif
 }