diff --git a/include/mcl/fp.hpp b/include/mcl/fp.hpp
index ca0c9d5..43749d9 100644
--- a/include/mcl/fp.hpp
+++ b/include/mcl/fp.hpp
@@ -105,6 +105,7 @@ public:
 	const Unit *getUnit() const { return v_; }
 	static inline size_t getUnitSize() { return op_.N; }
 	static inline size_t getBitSize() { return op_.bitSize; }
+	static inline size_t getByteSize() { return (op_.bitSize + 7) / 8; }
 	static inline const fp::Op& getOp() { return op_; }
 	void dump() const
 	{
@@ -221,7 +222,7 @@ public:
 	void setStr(const std::string& str, int ioMode = 0)
 	{
 		if (ioMode & (IoArray | IoArrayRaw)) {
-			const size_t n = getBitSize() / 8;
+			const size_t n = getByteSize();
 			if (str.size() != n) throw cybozu::Exception("FpT:setStr:bad size") << str.size() << n << ioMode;
 			if (ioMode & IoArrayRaw) {
 				memcpy(v_, str.c_str(), n);
@@ -289,15 +290,16 @@ public:
 	}
 	void getStr(std::string& str, int ioMode = 10) const
 	{
+		const size_t n = getByteSize();
 		if (ioMode & IoArrayRaw) {
-			str.resize(getBitSize() / 8);
+			str.resize(n);
 			memcpy(&str[0], v_, str.size());
 			return;
 		}
 		fp::Block b;
 		getBlock(b);
 		if (ioMode & IoArray) {
-			str.resize(getBitSize() / 8);
+			str.resize(n);
 			memcpy(&str[0], b.p, str.size());
 			return;
 		}
@@ -380,7 +382,7 @@ public:
 		int ioMode = fp::detectIoMode(getIoMode(), is);
 		std::string str;
 		if (ioMode & (IoArray | IoArrayRaw)) {
-			str.resize(getBitSize() / 8);
+			str.resize(getByteSize());
 			is.read(&str[0], str.size());
 		} else {
 			is >> str;
diff --git a/src/gen.cpp b/src/gen.cpp
index c74dee7..54f66e9 100644
--- a/src/gen.cpp
+++ b/src/gen.cpp
@@ -796,9 +796,9 @@ struct Code : public mcl::Generator {
 	{
 		this->privateFuncList = &privateFuncList;
 		gen_once();
-		uint32_t end = ((maxBitSize + unit - 1) / unit) * unit;
-		for (uint32_t i = 64; i <= end; i += unit) {
-			setBit(i);
+		uint32_t end = ((maxBitSize + unit - 1) / unit);
+		for (uint32_t n = 1; n <= end; n++) {
+			setBit(n * unit);
 			gen_all();
 			gen_addsub();
 			gen_mul();
diff --git a/test/fp_test.cpp b/test/fp_test.cpp
index 4ac1302..67aeb69 100644
--- a/test/fp_test.cpp
+++ b/test/fp_test.cpp
@@ -176,7 +176,7 @@ void ioModeTest()
 		}
 		std::stringstream ss;
 		ss << x;
-		CYBOZU_TEST_EQUAL(ss.str().size(), Fp::getBitSize() / 8);
+		CYBOZU_TEST_EQUAL(ss.str().size(), Fp::getByteSize());
 		Fp y;
 		ss >> y;
 		CYBOZU_TEST_EQUAL(x, y);