diff --git a/include/mcl/bn.h b/include/mcl/bn.h
index 08174ce..03756c5 100644
--- a/include/mcl/bn.h
+++ b/include/mcl/bn.h
@@ -94,8 +94,7 @@ typedef struct {
 } mclBnFp;
 
 typedef struct {
-	mclBnFp a;
-	mclBnFp b;
+	mclBnFp d[2];
 } mclBnFp2;
 
 #endif
diff --git a/test/bn_c_test.hpp b/test/bn_c_test.hpp
index f4fc79a..d6926a4 100644
--- a/test/bn_c_test.hpp
+++ b/test/bn_c_test.hpp
@@ -592,9 +592,9 @@ CYBOZU_TEST_AUTO(Fp2)
 {
 	mclBnFp2 x1, x2;
 	char buf[1024];
-	int ret = mclBnFp_setHashOf(&x1.a, "abc", 3);
+	int ret = mclBnFp_setHashOf(&x1.d[0], "abc", 3);
 	CYBOZU_TEST_ASSERT(ret == 0);
-	ret = mclBnFp_setHashOf(&x1.b, "xyz", 3);
+	ret = mclBnFp_setHashOf(&x1.d[1], "xyz", 3);
 	CYBOZU_TEST_ASSERT(ret == 0);
 	mclSize n = mclBnFp2_serialize(buf, sizeof(buf), &x1);
 	CYBOZU_TEST_ASSERT(n > 0);
@@ -621,8 +621,8 @@ CYBOZU_TEST_AUTO(mapToG2)
 {
 	mclBnFp2 x;
 	mclBnG2 P1, P2;
-	mclBnFp_setHashOf(&x.a, "abc", 3);
-	mclBnFp_clear(&x.b);
+	mclBnFp_setHashOf(&x.d[0], "abc", 3);
+	mclBnFp_clear(&x.d[1]);
 	int ret = mclBnFp2_mapToG2(&P1, &x);
 	CYBOZU_TEST_ASSERT(ret == 0);
 	mclBnG2_hashAndMapTo(&P2, "abc", 3);