diff --git a/include/mbedtls/x509.h b/include/mbedtls/x509.h
index 9ae825c..5808b4d 100644
--- a/include/mbedtls/x509.h
+++ b/include/mbedtls/x509.h
@@ -305,9 +305,11 @@
                      mbedtls_x509_buf *serial );
 int mbedtls_x509_get_ext( unsigned char **p, const unsigned char *end,
                   mbedtls_x509_buf *ext, int tag );
+#if defined(MBEDTLS_X509_INFO)
 int mbedtls_x509_sig_alg_gets( char *buf, size_t size, const mbedtls_x509_buf *sig_oid,
                        mbedtls_pk_type_t pk_alg, mbedtls_md_type_t md_alg,
                        const void *sig_opts );
+#endif
 int mbedtls_x509_key_size_helper( char *buf, size_t buf_size, const char *name );
 int mbedtls_x509_string_to_names( mbedtls_asn1_named_data **head, const char *name );
 int mbedtls_x509_set_extension( mbedtls_asn1_named_data **head, const char *oid, size_t oid_len,