diff --git a/tests/suites/test_suite_asn1write.function b/tests/suites/test_suite_asn1write.function
index f5fc025..b1e66ed 100644
--- a/tests/suites/test_suite_asn1write.function
+++ b/tests/suites/test_suite_asn1write.function
@@ -550,6 +550,9 @@
     }
     if (new_len == 0) {
         TEST_ASSERT(found->val.p == NULL);
+        /* If new_len != 0, then new_val != NULL and the length has been checked
+         * above by TEST_MEMORY_COMPARE(). But not here, so we need to check. */
+        TEST_EQUAL(found->val.len, 0);
     } else if (new_len == old_len) {
         TEST_ASSERT(found->val.p == old_val);
     } else {
@@ -583,8 +586,10 @@
     TEST_MEMORY_COMPARE(found->oid.p, found->oid.len, oid, oid_len);
     if (new_len == 0) {
         TEST_ASSERT(found->val.p == NULL);
+        TEST_EQUAL(found->val.len, 0);
     } else if (new_val == NULL) {
         TEST_ASSERT(found->val.p != NULL);
+        TEST_EQUAL(found->val.len, new_len);
     } else {
         TEST_ASSERT(found->val.p != new_val);
         TEST_MEMORY_COMPARE(found->val.p, found->val.len,