diff --git a/fido2/client.py b/fido2/client.py
index b921abd..41fff3e 100644
--- a/fido2/client.py
+++ b/fido2/client.py
@@ -47,10 +47,10 @@
 )
 from .cose import ES256
 from .rpid import verify_rp_id
-from .utils import sha256
+from .utils import sha256, _DataClassMapping
 from enum import IntEnum, unique
 from urllib.parse import urlparse
-from dataclasses import replace
+from dataclasses import replace, asdict
 from threading import Timer, Event
 from typing import (
     Type,
@@ -69,6 +69,16 @@
 logger = logging.getLogger(__name__)
 
 
+def ascbor(data):
+    if data is None:
+        return None
+    if isinstance(data, Sequence):
+        return [ascbor(d) for d in data]
+    if isinstance(data, _DataClassMapping):
+        # Remove empty values and do not serialize value
+        return {k: v for k, v in asdict(data).items() if v is not None}  # type: ignore
+
+
 class ClientError(Exception):
     @unique
     class ERR(IntEnum):
@@ -803,10 +813,10 @@ def make_credential(
         try:
             return self._backend.do_make_credential(
                 client_data,
-                rp,
-                options.user,
-                options.pub_key_cred_params,
-                options.exclude_credentials,
+                ascbor(rp),
+                ascbor(options.user),
+                ascbor(options.pub_key_cred_params),
+                ascbor(options.exclude_credentials),
                 options.extensions,
                 selection.require_resident_key,
                 selection.user_verification,
@@ -848,7 +858,7 @@ def get_assertion(
             return self._backend.do_get_assertion(
                 client_data,
                 options.rp_id,
-                options.allow_credentials,
+                ascbor(options.allow_credentials),
                 options.extensions,
                 options.user_verification,
                 event,