diff --git a/sml/src/sml_boolean.c b/sml/src/sml_boolean.c
index 2894e10..499f283 100644
--- a/sml/src/sml_boolean.c
+++ b/sml/src/sml_boolean.c
@@ -27,6 +27,9 @@ sml_boolean *sml_boolean_init(u8 b) {
 }
 
 sml_boolean *sml_boolean_parse(sml_buffer *buf) {
+	if (sml_buf_optional_is_skipped(buf)) {
+		return 0;
+	}
 	
 	int l;
 	if (sml_buf_get_next_type(buf) != SML_TYPE_BOOLEAN) {
diff --git a/test/src/sml_boolean_test.c b/test/src/sml_boolean_test.c
index 20ff5dc..474f363 100644
--- a/test/src/sml_boolean_test.c
+++ b/test/src/sml_boolean_test.c
@@ -57,6 +57,7 @@ TEST(sml_boolean, parse_optional) {
 	hex2binary("01", sml_buf_get_current_buf(buf));
 	sml_boolean *b = sml_boolean_parse(buf);
 	TEST_ASSERT_NULL(b);
+	TEST_ASSERT_FALSE(sml_buf_has_errors(buf));
 }
 
 TEST(sml_boolean, write_true) {
diff --git a/test/src/sml_octet_string_test.c b/test/src/sml_octet_string_test.c
index 8d1f659..8ee72ab 100644
--- a/test/src/sml_octet_string_test.c
+++ b/test/src/sml_octet_string_test.c
@@ -78,7 +78,12 @@ TEST(sml_octet_string, cmp) {
 	octet_string *s3 = sml_octet_string_init((unsigned char *)"Hallo", 5);
 	
 	TEST_ASSERT_TRUE(sml_octet_string_cmp(s1, s2) != 0);
-	TEST_ASSERT_TRUE(sml_octet_string_cmp(s1, s3) == 0);
+	TEST_ASSERT_EQUAL(0, sml_octet_string_cmp(s1, s3));
+}
+
+TEST(sml_octet_string, cmp_with_hex) {
+	octet_string *s = sml_octet_string_init((unsigned char *)"Hallo", 5);
+	TEST_ASSERT_EQUAL(0, sml_octet_string_cmp_with_hex(s, "48616C6C6F"));
 }
 
 TEST_GROUP_RUNNER(sml_octet_string) {
@@ -89,6 +94,7 @@ TEST_GROUP_RUNNER(sml_octet_string) {
 	RUN_TEST_CASE(sml_octet_string, write);
 	RUN_TEST_CASE(sml_octet_string, write_optional);
 	RUN_TEST_CASE(sml_octet_string, cmp);
+	RUN_TEST_CASE(sml_octet_string, cmp_with_hex);
 }