diff --git a/include/mcl/ec.hpp b/include/mcl/ec.hpp
index 708b854..9a802e7 100644
--- a/include/mcl/ec.hpp
+++ b/include/mcl/ec.hpp
@@ -504,12 +504,18 @@ public:
 			return;
 		}
 		if (isPzOne) {
-			R.z = H;
+			if (isQzOne) {
+				R.z = H;
+			} else {
+				Fp::mul(R.z, H, Q.z);
+			}
 		} else {
-			Fp::mul(R.z, P.z, H);
-		}
-		if (!isQzOne) {
-			R.z *= Q.z;
+			if (isQzOne) {
+				Fp::mul(R.z, P.z, H);
+			} else {
+				Fp::mul(R.z, P.z, Q.z);
+				R.z *= H;
+			}
 		}
 		Fp::sqr(H3, H); // H^2
 		Fp::sqr(R.y, r); // r^2
@@ -994,7 +1000,7 @@ public:
 	bool operator<=(const EcT& rhs) const { return !operator>(rhs); }
 	static inline void mulArray(EcT& z, const EcT& x, const fp::Unit *y, size_t yn, bool isNegative, bool constTime = false)
 	{
-		if (!constTime && yn == 1 && *y <= 16 && !isNegative) {
+		if (!constTime && yn == 1) {
 			if (mulSmallInt(z, x, static_cast<int>(*y), isNegative)) return;
 		}
 		if (mulArrayGLV && (constTime || yn > 1)) {
diff --git a/test/ec_test.cpp b/test/ec_test.cpp
index 7999443..3f1e8d4 100644
--- a/test/ec_test.cpp
+++ b/test/ec_test.cpp
@@ -205,11 +205,43 @@ struct Test {
 		Ec R;
 		R.clear();
 		for (int i = 0; i < 100; i++) {
-			Ec::mul(Q, P, i);
+			Q = P;
+			Ec::mul(Q, Q, i);
 			CYBOZU_TEST_EQUAL(Q, R);
+			Q = P;
+			if (Ec::mulSmallInt(Q, Q, i, false)) {
+				CYBOZU_TEST_EQUAL(Q, R);
+			}
 			R += P;
 		}
 	}
+	void add() const
+	{
+		Fp x(para.gx);
+		Fp y(para.gy);
+		Ec P1(x, y);
+		Ec P2, Q1, Q2;
+		Ec::dbl(P1, P1);
+		Ec::normalize(P2, P1);
+		Q1 = P1 + P1;
+		Ec::normalize(Q2, Q1);
+		Ec Ptbl[] = { P1, P2 };
+		Ec Qtbl[] = { Q1, Q2 };
+		for (int i = 0; i < 2; i++) {
+			for (int j = 0; j < 2; j++) {
+				Ec R1, R2, R3, R4;
+				R1 = Ptbl[i];
+				R2 = Qtbl[i];
+				Ec::add(R3, R1, R2);
+				Ec::add(R1, R1, R2);
+				CYBOZU_TEST_EQUAL(R1, R3);
+				R1 = Ptbl[i];
+				R2 = Qtbl[i];
+				Ec::add(R2, R1, R2);
+				CYBOZU_TEST_EQUAL(R2, R3);
+			}
+		}
+	}
 
 	void neg_mul() const
 	{
@@ -220,8 +252,13 @@ struct Test {
 		Ec R;
 		R.clear();
 		for (int i = 0; i < 100; i++) {
-			Ec::mul(Q, P, -i);
+			Q = P;
+			Ec::mul(Q, Q, -i);
 			CYBOZU_TEST_EQUAL(Q, R);
+			Q = P;
+			if (Ec::mulSmallInt(Q, Q, -i, true)) {
+				CYBOZU_TEST_EQUAL(Q, R);
+			}
 			R -= P;
 		}
 	}
@@ -476,6 +513,7 @@ mul 499.00usec
 		cstr();
 		ope();
 		mul();
+		add();
 		neg_mul();
 		mul_fp();
 		squareRoot();