diff --git a/include/mcl/fp_tower.hpp b/include/mcl/fp_tower.hpp
index d4536a9..a2cf930 100644
--- a/include/mcl/fp_tower.hpp
+++ b/include/mcl/fp_tower.hpp
@@ -695,27 +695,6 @@ struct Fp2DblT {
 		FpDbl::neg(y.a, x.a);
 		FpDbl::neg(y.b, x.b);
 	}
-	static void mul_xi_1A(Unit *py, const Unit *px)
-	{
-		Fp2Dbl& y = castD(py);
-		const Fp2Dbl& x = castD(px);
-		FpDbl t;
-		FpDbl::add(t, x.a, x.b);
-		FpDbl::sub(y.a, x.a, x.b);
-		y.b = t;
-	}
-	static void mul_xi_genericA(Unit *py, const Unit *px)
-	{
-		const uint32_t xi_a = Fp2::get_xi_a();
-		Fp2Dbl& y = castD(py);
-		const Fp2Dbl& x = castD(px);
-		FpDbl t;
-		FpDbl::mulUnit(t, x.a, xi_a);
-		FpDbl::sub(t, t, x.b);
-		FpDbl::mulUnit(y.b, x.b, xi_a);
-		FpDbl::add(y.b, y.b, x.a);
-		y.a = t;
-	}
 	static void mulPre(Fp2DblT& z, const Fp2& x, const Fp2& y)
 	{
 		Fp::getOp().fp2Dbl_mulPreA_(z.a.v_, x.getUnit(), y.getUnit());
@@ -804,6 +783,27 @@ private:
 		Fp::sub(t1, x.a, x.b); // a - b
 		FpDbl::mulPre(y.a, t1, t2); // (a + b)(a - b)
 	}
+	static void mul_xi_1A(Unit *py, const Unit *px)
+	{
+		Fp2Dbl& y = castD(py);
+		const Fp2Dbl& x = castD(px);
+		FpDbl t;
+		FpDbl::add(t, x.a, x.b);
+		FpDbl::sub(y.a, x.a, x.b);
+		y.b = t;
+	}
+	static void mul_xi_genericA(Unit *py, const Unit *px)
+	{
+		const uint32_t xi_a = Fp2::get_xi_a();
+		Fp2Dbl& y = castD(py);
+		const Fp2Dbl& x = castD(px);
+		FpDbl t;
+		FpDbl::mulUnit(t, x.a, xi_a);
+		FpDbl::sub(t, t, x.b);
+		FpDbl::mulUnit(y.b, x.b, xi_a);
+		FpDbl::add(y.b, y.b, x.a);
+		y.a = t;
+	}
 };
 
 template<class Fp> Fp2T<Fp> Fp2T<Fp>::g[Fp2T<Fp>::gN];
diff --git a/test/common_test.hpp b/test/common_test.hpp
index 74a745c..5deb9f1 100644
--- a/test/common_test.hpp
+++ b/test/common_test.hpp
@@ -163,10 +163,11 @@ void testABCD()
 
 void testFp2Dbl_mul_xi1()
 {
-	if (Fp2::get_xi_a() != 1) return;
+	const uint32_t xi_a = Fp2::get_xi_a();
+	if (xi_a != 1) return;
 	puts("testFp2Dbl_mul_xi1");
 	cybozu::XorShift rg;
-	for (int i = 0; i < 100; i++) {
+	for (int i = 0; i < 10; i++) {
 		Fp a1, a2;
 		a1.setByCSPRNG(rg);
 		a2.setByCSPRNG(rg);
@@ -176,7 +177,12 @@ void testFp2Dbl_mul_xi1()
 		a2.setByCSPRNG(rg);
 		FpDbl::mulPre(x.b, a1, a2);
 		Fp2Dbl ok;
-		Fp2Dbl::mul_xi_1C(ok, x);
+		{
+			FpDbl::mulUnit(ok.a, x.a, xi_a);
+			ok.a -= x.b;
+			FpDbl::mulUnit(ok.b, x.b, xi_a);
+			ok.b += x.a;
+		}
 		Fp2Dbl::mul_xi(x, x);
 		CYBOZU_TEST_EQUAL_ARRAY(ok.a.getUnit(), x.a.getUnit(), ok.a.getUnitSize());
 		CYBOZU_TEST_EQUAL_ARRAY(ok.b.getUnit(), x.b.getUnit(), ok.b.getUnitSize());