diff --git a/library/x509.c b/library/x509.c
index 62bc39b..18e6a18 100644
--- a/library/x509.c
+++ b/library/x509.c
@@ -875,8 +875,14 @@
             s[0] = '#';
 
             asn1_len_p = asn1_tag_len_buf + 10;
-            asn1_len_size = mbedtls_asn1_write_len(&asn1_len_p, asn1_tag_len_buf, name->val.len);
-            asn1_tag_size = mbedtls_asn1_write_tag(&asn1_len_p, asn1_tag_len_buf, name->val.tag);
+            if((ret = mbedtls_asn1_write_len(&asn1_len_p, asn1_tag_len_buf, name->val.len)) < 0) {
+                return MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+            }
+            asn1_len_size = ret;
+            if((ret = mbedtls_asn1_write_tag(&asn1_len_p, asn1_tag_len_buf, name->val.tag)) < 0) {
+                return MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+            }
+            asn1_tag_size = ret;
             asn1_tag_len_buf_start = 10 - asn1_len_size - asn1_tag_size;
             for (i = 0, j = 1; i < asn1_len_size + asn1_tag_size; i++) {
                 if (j + 1 >= sizeof(s) - 1) {