diff --git a/library/x509_create.c b/library/x509_create.c
index daf17a6..dba76a9 100644
--- a/library/x509_create.c
+++ b/library/x509_create.c
@@ -242,7 +242,7 @@
     int parse_ret = 0;
     const char *s = name, *c = s;
     const char *end = s + strlen(s);
-    mbedtls_asn1_buf oid = { .p = NULL, .len = 0, .tag = 5 };
+    mbedtls_asn1_buf oid = { .p = NULL, .len = 0, .tag = MBEDTLS_ASN1_NULL };
     const x509_attr_descriptor_t *attr_descr = NULL;
     int in_attr_type = 1;
     int tag;