diff --git a/lib/src/gkcrypt.c b/lib/src/gkcrypt.c
index 0d58b03..fce33eb 100644
--- a/lib/src/gkcrypt.c
+++ b/lib/src/gkcrypt.c
@@ -191,12 +191,8 @@ CHIAKI_EXPORT ChiakiErrorCode chiaki_gkcrypt_gmac(ChiakiGKCrypt *gkcrypt, size_t
 
 	uint8_t *gmac_key = gkcrypt->key_gmac_current;
 	uint8_t gmac_key_tmp[CHIAKI_GKCRYPT_BLOCK_SIZE];
-	uint64_t key_index = key_pos / CHIAKI_GKCRYPT_GMAC_KEY_REFRESH_KEY_POS;
-	if(key_index != (key_pos + buf_size - 1) / CHIAKI_GKCRYPT_GMAC_KEY_REFRESH_KEY_POS)
-	{
-		CHIAKI_LOGD(gkcrypt->log, "SPLIT! %u != %u\n", key_index, (key_pos + buf_size - 1) / CHIAKI_GKCRYPT_GMAC_KEY_REFRESH_KEY_POS);
-	}
-	// TODO: what to do if (key_pos / CHIAKI_GKCRYPT_GMAC_KEY_REFRESH_KEY_POS) != ((key_pos + buf_size) / CHIAKI_GKCRYPT_GMAC_KEY_REFRESH_KEY_POS)?
+	uint64_t key_index = (key_pos > 0 ? key_pos - 1 : 0) / CHIAKI_GKCRYPT_GMAC_KEY_REFRESH_KEY_POS;
+
 	if(key_index > gkcrypt->key_gmac_index_current)
 	{
 		chiaki_gkcrypt_gen_new_gmac_key(gkcrypt, key_index);
diff --git a/test/gkcrypt.c b/test/gkcrypt.c
index 495de9a..d0ec4ab 100644
--- a/test/gkcrypt.c
+++ b/test/gkcrypt.c
@@ -280,6 +280,50 @@ static MunitResult test_gmac_split(const MunitParameter params[], void *user)
 	return MUNIT_OK;
 }
 
+static MunitResult test_gmac_multiple_of_key_refresh(const MunitParameter params[], void *user)
+{
+	static const uint8_t handshake_key[] = { 0x70, 0x58, 0x37, 0x50, 0x91, 0xea, 0xd1, 0x37, 0x71, 0x58, 0xec, 0xb3, 0xb, 0xea, 0x23, 0x87 };
+	static const uint8_t ecdh_secret[] = { 0x3c, 0x3a, 0xf0, 0xec, 0xd6, 0x33, 0x1b, 0xb1, 0x6d, 0x24, 0x4f, 0x48, 0x19, 0xde, 0x6, 0x3d,
+										0xc7, 0xe, 0xac, 0x95, 0x70, 0xac, 0x24, 0x92, 0x86, 0xa7, 0x24, 0xd0, 0x7a, 0x37, 0x55, 0x52 };
+
+	static const uint8_t data[] = { 0x3, 0x11, 0xa4, 0x11, 0xa5, 00, 0x2, 0x50, 0x21, 0x5, 00, 00, 00, 00, 00, 0x6b,
+									0x1d, 0xe0, 00, 0x83, 0xf1, 0xc4, 0x79, 0x71, 0xe4, 0x67, 0x7c, 0xcc, 0xb7, 0x92, 0x7, 0x8b,
+									0xba, 0x8a, 0x8, 0xd6, 0x62, 0xf5, 0x7, 0x5d, 0x4a, 0x20, 0x14, 0xb3, 0xe7, 0xe, 0x5c, 0x77,
+									0xfd, 0x6d, 0x60, 0xa3, 0xc5, 0x48, 0xa9, 0xc0, 0x61, 0xf9, 0x84, 0xf6, 0x37, 0x62, 0xac, 0xbc,
+									0x1f, 0x5d, 0xe4, 0x40, 0x90, 0x54, 0x71, 0x37, 0xab, 0x33, 0x7e, 0xaa, 0xa5, 0xf4, 0xc4, 0x9,
+									0x3, 0xf4, 0xb6, 0xa1, 0x2f, 0x2, 0x27, 0x53, 0xc6, 0xa5, 0xb1, 0x9c, 0x8f, 0xb4, 0x69, 0xd6,
+									0x5c, 0x7f, 0x79, 0x5f, 0x14, 0x47, 0xcc, 0xa8, 0x8b, 0x37, 0xf7, 0x77, 0x6d, 0x1, 0xf4, 0x5b,
+									0x59, 0xca, 0x96, 0x73, 0xa, 0x20, 0xf3, 0x7a, 0xd1, 0xd2, 0x7f, 0xfe, 0xb6, 0x66, 0xf4, 0xdb,
+									0x10, 0xaf, 0xf3, 0x7, 0xee, 0x49, 0x8a, 0xa1, 0xa5, 0x73, 0xd8, 0x23, 0x83, 0xe, 0xc, 0xc,
+									0x3a, 0x49, 0xdc, 0xd8, 0xc, 0xc8, 0xe4, 0xb6, 0xf2, 0x3c, 0x6d, 0x25, 0x6a, 0x7d, 0xa0, 0x1c,
+									0x3a, 0x8e, 0xf, 0x3f, 0x25, 0x47, 0x11, 0x89, 0x67, 0xc4, 0xf9, 0xac, 0xc7, 0xe2, 0x93, 0x74,
+									0xc6, 0xfb, 0xdd, 0x48, 0x57, 0xae, 0x53, 0xe2, 0xf4, 0x17, 0x80, 0x62, 0xf3, 0x9, 0xd8, 0xd4,
+									0x7a, 0x46, 0x6b, 0x8, 0x76, 0x9c, 0x29, 0x81, 0x91, 0x4e, 0x57, 0xaf, 0x70, 0xb6, 0x32, 0x78,
+									0x98, 0x9e, 0x85, 0xf2, 0xe3, 0x69, 0x15, 0xaf, 0xd4, 0x32, 0x54, 0xf, 0xd4, 0xa2, 0xfc, 0xf5,
+									0x36, 0xdc, 0x6, 0x45, 0xf4, 0x6, 0xa3, 0x38, 0x21, 0x2, 0xfd, 0xf0, 0x51, 0x75, 0xea, 0xb1,
+									0xf6, 0x8e, 0x39, 0x35, 0xfd, 0x75, 0x74, 0xad, 0xbc, 0x3e, 0xfb, 0xee, 0x7d, 0xf, 0x2d, 0x76,
+									0xbe, 0xfd, 0xee };
+
+	static const uint8_t crypt_index = 3;
+	static const size_t key_pos = 0x6b1de0; // % CHIAKI_GKCRYPT_GMAC_KEY_REFRESH_KEY_POS == 0
+	static const uint8_t gmac_expected[] = { 0x20, 0xcc, 0xa5, 0xf1 };
+
+	ChiakiLog log;
+	ChiakiGKCrypt gkcrypt;
+	chiaki_gkcrypt_init(&gkcrypt, &log, 0, crypt_index, handshake_key, ecdh_secret);
+
+	uint8_t gmac[CHIAKI_GKCRYPT_GMAC_SIZE];
+	ChiakiErrorCode err = chiaki_gkcrypt_gmac(&gkcrypt, key_pos, data, sizeof(data), gmac);
+	if(err != CHIAKI_ERR_SUCCESS)
+		return MUNIT_ERROR;
+
+	munit_assert_memory_equal(sizeof(gmac), gmac, gmac_expected);
+
+	chiaki_gkcrypt_fini(&gkcrypt);
+
+	return MUNIT_OK;
+}
+
 
 MunitTest tests_gkcrypt[] = {
 	{
@@ -330,5 +374,13 @@ MunitTest tests_gkcrypt[] = {
 		MUNIT_TEST_OPTION_NONE,
 		NULL
 	},
+	{
+		"/gmac_multiple_of_key_refresh",
+		test_gmac_multiple_of_key_refresh,
+		NULL,
+		NULL,
+		MUNIT_TEST_OPTION_NONE,
+		NULL
+	},
 	{ NULL, NULL, NULL, NULL, MUNIT_TEST_OPTION_NONE, NULL }
 };
\ No newline at end of file