diff --git a/library/asn1write.c b/library/asn1write.c
index 0b487dc..f9c3830 100644
--- a/library/asn1write.c
+++ b/library/asn1write.c
@@ -195,24 +195,33 @@
                                             const char *oid, size_t oid_len,
                                             size_t par_len)
 {
+    return mbedtls_asn1_write_algorithm_identifier_ext(p, start, oid, oid_len, par_len, 1);
+}
+
+int mbedtls_asn1_write_algorithm_identifier_ext(unsigned char **p, unsigned char *start,
+                                                const char *oid, size_t oid_len,
+                                                size_t par_len, int has_par)
+{
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
     size_t len = 0;
 
-    if (par_len == 0) {
-        MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_null(p, start));
-    } else {
-        len += par_len;
+    if (has_par) {
+        if (par_len == 0) {
+            MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_null(p, start));
+        } else {
+            len += par_len;
+        }
     }
 
     MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_oid(p, start, oid, oid_len));
 
     MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(p, start, len));
     MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(p, start,
-                                                     MBEDTLS_ASN1_CONSTRUCTED |
-                                                     MBEDTLS_ASN1_SEQUENCE));
+                                                    MBEDTLS_ASN1_CONSTRUCTED |
+                                                    MBEDTLS_ASN1_SEQUENCE));
 
     return (int) len;
-}
+ }
 
 int mbedtls_asn1_write_bool(unsigned char **p, unsigned char *start, int boolean)
 {