diff --git a/test/asn1_encode_test.c b/test/asn1_encode_test.c
index 68a0696..763c427 100644
--- a/test/asn1_encode_test.c
+++ b/test/asn1_encode_test.c
@@ -38,6 +38,9 @@
 static unsigned char t_one[] = {
     0x01
 };
+static unsigned char t_one_neg[] = {
+    0xff
+};
 static unsigned char t_longundef[] = {
     0x7f, 0xff, 0xff, 0xff
 };
@@ -95,6 +98,7 @@
     CUSTOM_DATA(t_zero),
     CUSTOM_DATA(t_longundef),
     CUSTOM_DATA(t_one),
+    CUSTOM_DATA(t_one_neg),
     CUSTOM_DATA(t_9bytes_1),
     CUSTOM_DATA(t_8bytes_1),
     CUSTOM_DATA(t_8bytes_2),
@@ -194,6 +198,7 @@
     { 0xff, 0, 1 }, { 0, 0, 0 }, /* t_zero */
     { 0, 0, 0 }, { 0xff, 1, 0x7fffffff }, /* t_longundef */
     CUSTOM_EXPECTED_SUCCESS(1, 1), /* t_one */
+    CUSTOM_EXPECTED_SUCCESS(-1, -1), /* t_one_neg */
     CUSTOM_EXPECTED_FAILURE,     /* t_9bytes_1 */
     CUSTOM_EXPECTED_FAILURE,     /* t_8bytes_1 */
     CUSTOM_EXPECTED_FAILURE,     /* t_8bytes_2 */
@@ -228,6 +233,7 @@
     { 0xff, 0, 1 }, { 0, 0, 0 }, /* t_zero */
     { 0, 0, 0 }, { 0xff, 1, 0x7fffffff }, /* t_longundef */
     CUSTOM_EXPECTED_SUCCESS(1, 1), /* t_one */
+    CUSTOM_EXPECTED_SUCCESS(-1, -1), /* t_one_neg */
     CUSTOM_EXPECTED_FAILURE,     /* t_9bytes_1 */
     CUSTOM_EXPECTED_FAILURE,     /* t_8bytes_1 */
     CUSTOM_EXPECTED_SUCCESS(LONG_MAX, LONG_MAX), /* t_8bytes_2 */
@@ -279,6 +285,7 @@
     CUSTOM_EXPECTED_SUCCESS(0, 0), /* t_zero */
     CUSTOM_EXPECTED_SUCCESS(ASN1_LONG_UNDEF, ASN1_LONG_UNDEF), /* t_zero */
     CUSTOM_EXPECTED_SUCCESS(1, 1), /* t_one */
+    CUSTOM_EXPECTED_SUCCESS(-1, -1), /* t_one_neg */
     CUSTOM_EXPECTED_FAILURE,     /* t_9bytes_1 */
     CUSTOM_EXPECTED_FAILURE,     /* t_8bytes_1 */
     CUSTOM_EXPECTED_FAILURE,     /* t_8bytes_2 */
@@ -325,6 +332,7 @@
     CUSTOM_EXPECTED_SUCCESS(0, 0), /* t_zero */
     CUSTOM_EXPECTED_SUCCESS(ASN1_LONG_UNDEF, ASN1_LONG_UNDEF), /* t_zero */
     CUSTOM_EXPECTED_SUCCESS(1, 1), /* t_one */
+    CUSTOM_EXPECTED_FAILURE,     /* t_one_neg (illegal negative value) */
     CUSTOM_EXPECTED_FAILURE,     /* t_9bytes_1 */
     CUSTOM_EXPECTED_FAILURE,     /* t_8bytes_1 */
     CUSTOM_EXPECTED_FAILURE,     /* t_8bytes_2 */
@@ -371,6 +379,7 @@
     CUSTOM_EXPECTED_SUCCESS(0, 0), /* t_zero */
     CUSTOM_EXPECTED_SUCCESS(ASN1_LONG_UNDEF, ASN1_LONG_UNDEF), /* t_zero */
     CUSTOM_EXPECTED_SUCCESS(1, 1), /* t_one */
+    CUSTOM_EXPECTED_SUCCESS(-1, -1), /* t_one_neg */
     CUSTOM_EXPECTED_FAILURE,     /* t_9bytes_1 */
     CUSTOM_EXPECTED_FAILURE,     /* t_8bytes_1 (too large positive) */
     CUSTOM_EXPECTED_SUCCESS(INT64_MAX, INT64_MAX), /* t_8bytes_2 */
@@ -418,6 +427,7 @@
     CUSTOM_EXPECTED_SUCCESS(0, 0), /* t_zero */
     CUSTOM_EXPECTED_SUCCESS(ASN1_LONG_UNDEF, ASN1_LONG_UNDEF), /* t_zero */
     CUSTOM_EXPECTED_SUCCESS(1, 1), /* t_one */
+    CUSTOM_EXPECTED_FAILURE,     /* t_one_neg (illegal negative value) */
     CUSTOM_EXPECTED_FAILURE,     /* t_9bytes_1 */
     CUSTOM_EXPECTED_SUCCESS((uint64_t)INT64_MAX+1, (uint64_t)INT64_MAX+1),
                                  /* t_8bytes_1 */