diff --git a/include/mbedtls/x509.h b/include/mbedtls/x509.h
index b63e864..054ff2e 100644
--- a/include/mbedtls/x509.h
+++ b/include/mbedtls/x509.h
@@ -110,6 +110,28 @@
 /* \} addtogroup x509_module */
 
 /*
+ * X.509 v3 Subject Alternative Name types.
+ *      otherName                       [0]     OtherName,
+ *      rfc822Name                      [1]     IA5String,
+ *      dNSName                         [2]     IA5String,
+ *      x400Address                     [3]     ORAddress,
+ *      directoryName                   [4]     Name,
+ *      ediPartyName                    [5]     EDIPartyName,
+ *      uniformResourceIdentifier       [6]     IA5String,
+ *      iPAddress                       [7]     OCTET STRING,
+ *      registeredID                    [8]     OBJECT IDENTIFIER
+ */
+#define MBEDTLS_X509_SAN_OTHER_NAME                      0
+#define MBEDTLS_X509_SAN_RFC822_NAME                     1
+#define MBEDTLS_X509_SAN_DNS_NAME                        2
+#define MBEDTLS_X509_SAN_X400_ADDRESS_NAME               3
+#define MBEDTLS_X509_SAN_DIRECTORY_NAME                  4
+#define MBEDTLS_X509_SAN_EDI_PARTY_NAME                  5
+#define MBEDTLS_X509_SAN_UNIFORM_RESOURCE_IDENTIFIER     6
+#define MBEDTLS_X509_SAN_IP_ADDRESS                      7
+#define MBEDTLS_X509_SAN_REGISTERED_ID                   8
+
+/*
  * X.509 v3 Key Usage Extension flags
  * Reminder: update x509_info_key_usage() when adding new flags.
  */