diff --git a/etebase_fastapi/authentication.py b/etebase_fastapi/authentication.py
index 04aec31..2f5a2f1 100644
--- a/etebase_fastapi/authentication.py
+++ b/etebase_fastapi/authentication.py
@@ -25,7 +25,7 @@ from django_etebase.token_auth.models import get_default_expiry
 from django_etebase.utils import create_user, get_user_queryset, CallbackContext
 from .exceptions import AuthenticationFailed, transform_validation_error, HttpError
 from .msgpack import MsgpackRoute
-from .utils import BaseModel, permission_responses, msgpack_encode, msgpack_decode 
+from .utils import BaseModel, permission_responses, msgpack_encode, msgpack_decode
 
 User = get_user_model()
 token_scheme = APIKeyHeader(name="Authorization")
@@ -63,7 +63,7 @@ class UserOut(BaseModel):
 
     @classmethod
     def from_orm(cls: t.Type["UserOut"], obj: User) -> "UserOut":
-        return cls(pubkey=obj.userinfo.pubkey, encryptedContent=obj.userinfo.encryptedContent)
+        return cls(pubkey=bytes(obj.userinfo.pubkey), encryptedContent=bytes(obj.userinfo.encryptedContent))
 
 
 class LoginOut(BaseModel):
@@ -228,14 +228,15 @@ async def is_etebase():
 
 @authentication_router.post("/login_challenge/", response_model=LoginChallengeOut)
 async def login_challenge(user: User = Depends(get_login_user)):
-    enc_key = get_encryption_key(user.userinfo.salt)
+    salt = bytes(user.userinfo.salt)
+    enc_key = get_encryption_key(salt)
     box = nacl.secret.SecretBox(enc_key)
     challenge_data = {
         "timestamp": int(datetime.now().timestamp()),
         "userId": user.id,
     }
     challenge = bytes(box.encrypt(msgpack_encode(challenge_data), encoder=nacl.encoding.RawEncoder))
-    return LoginChallengeOut(salt=user.userinfo.salt, challenge=challenge, version=user.userinfo.version)
+    return LoginChallengeOut(salt=salt, challenge=challenge, version=user.userinfo.version)
 
 
 @authentication_router.post("/login/", response_model=LoginOut)
diff --git a/etebase_fastapi/collection.py b/etebase_fastapi/collection.py
index e6c10c3..74730ff 100644
--- a/etebase_fastapi/collection.py
+++ b/etebase_fastapi/collection.py
@@ -58,7 +58,7 @@ class CollectionItemRevisionInOut(BaseModel):
                     chunks.append((chunk_obj.uid, f.read()))
             else:
                 chunks.append((chunk_obj.uid,))
-        return cls(uid=obj.uid, meta=obj.meta, deleted=obj.deleted, chunks=chunks)
+        return cls(uid=obj.uid, meta=bytes(obj.meta), deleted=obj.deleted, chunks=chunks)
 
 
 class CollectionItemCommon(BaseModel):
@@ -103,8 +103,8 @@ class CollectionOut(CollectionCommon):
         member: models.CollectionMember = obj.members.get(user=context.user)
         collection_type = member.collectionType
         ret = cls(
-            collectionType=collection_type and collection_type.uid,
-            collectionKey=member.encryptionKey,
+            collectionType=collection_type and bytes(collection_type.uid),
+            collectionKey=bytes(member.encryptionKey),
             accessLevel=member.accessLevel,
             stoken=obj.stoken,
             item=CollectionItemOut.from_orm_context(obj.main_item, context),
diff --git a/etebase_fastapi/invitation.py b/etebase_fastapi/invitation.py
index 39460a9..9e731bc 100644
--- a/etebase_fastapi/invitation.py
+++ b/etebase_fastapi/invitation.py
@@ -32,6 +32,10 @@ class UserInfoOut(BaseModel):
     class Config:
         orm_mode = True
 
+    @classmethod
+    def from_orm(cls: t.Type["UserInfoOut"], obj: models.UserInfo) -> "UserInfoOut":
+        return cls(pubkey=bytes(obj.pubkey))
+
 
 class CollectionInvitationAcceptIn(BaseModel):
     collectionType: bytes
@@ -69,8 +73,8 @@ class CollectionInvitationOut(CollectionInvitationCommon):
             username=obj.user.username,
             collection=obj.collection.uid,
             fromUsername=obj.fromMember.user.username,
-            fromPubkey=obj.fromMember.user.userinfo.pubkey,
-            signedEncryptionKey=obj.signedEncryptionKey,
+            fromPubkey=bytes(obj.fromMember.user.userinfo.pubkey),
+            signedEncryptionKey=bytes(obj.signedEncryptionKey),
         )