diff --git a/src/ohmyapi/builtin/auth/models.py b/src/ohmyapi/builtin/auth/models.py
index 7628c4f..c0983c7 100644
--- a/src/ohmyapi/builtin/auth/models.py
+++ b/src/ohmyapi/builtin/auth/models.py
@@ -1,20 +1,22 @@
-from functools import wraps
-from typing import Optional, List
 from ohmyapi.router import HTTPException
 from ohmyapi.db import Model, field, pre_save, pre_delete
+
+from functools import wraps
+from typing import Optional, List
 from passlib.context import CryptContext
 from tortoise.contrib.pydantic import pydantic_queryset_creator
+from uuid import UUID
 
 pwd_context = CryptContext(schemes=["argon2"], deprecated="auto")
 
 
 class Group(Model):
-    id: str = field.data.UUIDField(pk=True)
+    id: UUID = field.data.UUIDField(pk=True)
     name: str = field.CharField(max_length=42, index=True)
 
 
 class User(Model):
-    id: str = field.data.UUIDField(pk=True)
+    id: UUID = field.data.UUIDField(pk=True)
     email: str = field.CharField(max_length=255, unique=True, index=True)
     username: str = field.CharField(max_length=150, unique=True)
     password_hash: str = field.CharField(max_length=128)
diff --git a/src/ohmyapi/db/model/model.py b/src/ohmyapi/db/model/model.py
index eb0b504..e67b81e 100644
--- a/src/ohmyapi/db/model/model.py
+++ b/src/ohmyapi/db/model/model.py
@@ -1,6 +1,27 @@
+from pydantic_core import core_schema
+from pydantic import GetCoreSchemaHandler
 from tortoise import fields as field
 from tortoise.models import Model as TortoiseModel
 from tortoise.contrib.pydantic import pydantic_model_creator, pydantic_queryset_creator
+from uuid import UUID
+
+
+def __uuid_schema_monkey_patch(cls, source_type, handler):
+    # Always treat UUID as string schema
+    return core_schema.no_info_after_validator_function(
+        # Accept UUID or str, always return UUID internally
+        lambda v: v if isinstance(v, UUID) else UUID(str(v)),
+        core_schema.union_schema([
+            core_schema.str_schema(),
+            core_schema.is_instance_schema(UUID),
+        ]),
+        # But when serializing, always str()
+        serialization=core_schema.plain_serializer_function_ser_schema(str, when_used="always"),
+    )
+
+
+# Monkey-patch UUID
+UUID.__get_pydantic_core_schema__ = classmethod(__uuid_schema_monkey_patch)
 
 
 class ModelMeta(type(TortoiseModel)):