diff --git a/kui/pydantic_compatible.py b/kui/pydantic_compatible.py
index c7857db09..d3eb03c79 100644
--- a/kui/pydantic_compatible.py
+++ b/kui/pydantic_compatible.py
@@ -30,7 +30,7 @@ def validate_model(model: Type[BaseModel], v: Any) -> Tuple[Type[BaseModel], Any
         if hasattr(res, "__root__"):
             return model, res.__root__
         else:
-            return model, res.dict(by_alias=False)
+            return model, res.__dict__
 
     def get_model_fields(model: Type[BaseModel]) -> Dict[str, ModelField]:  # type: ignore
         return model.__fields__  # type: ignore
@@ -53,7 +53,7 @@ def validate_model(model: Type[BaseModel], v: Any) -> Tuple[Type[BaseModel], Any
         if isinstance(res, RootModel):
             return model, res.root
         else:
-            return model, res.model_dump(by_alias=False)
+            return model, res.__dict__
 
     def get_model_fields(model: Type[BaseModel]) -> Dict[str, FieldInfo]:  # type: ignore
         return model.model_fields
diff --git a/tests/asgi/test_parameters.py b/tests/asgi/test_parameters.py
index 878dc50e5..36b036d02 100644
--- a/tests/asgi/test_parameters.py
+++ b/tests/asgi/test_parameters.py
@@ -4,6 +4,7 @@
 import httpx
 import pytest
 from async_asgi_testclient import TestClient
+from pydantic import BaseModel
 from typing_extensions import Annotated
 
 from kui.asgi import (
@@ -255,3 +256,24 @@ async def upload_file(file: Annotated[UploadFile, Body(...)]):
 
         resp = await client.post("/", files={"file0": io.BytesIO(b"123")})
         assert resp.status_code == 422
+
+
+@pytest.mark.asyncio
+async def test_parameters_nest_model():
+    app = Kui()
+
+    class User(BaseModel):
+        name: str
+        age: int
+
+    @app.router.http.post("/")
+    async def create_user(user: Annotated[User, Body(...)]):
+        assert user.age >= 18
+        return user
+
+    async with httpx.AsyncClient(app=app, base_url="http://testserver") as client:
+        resp = await client.post("/", json={"user": {"name": "aber", "age": 18}})
+        assert resp.json() == {"name": "aber", "age": 18}
+
+        resp = await client.post("/", json={"name": "aber", "age": 18})
+        assert resp.status_code == 422
diff --git a/tests/wsgi/test_parameters.py b/tests/wsgi/test_parameters.py
index 9c3043e21..f38824cbb 100644
--- a/tests/wsgi/test_parameters.py
+++ b/tests/wsgi/test_parameters.py
@@ -3,6 +3,7 @@
 
 import httpx
 from httpx import Client
+from pydantic import BaseModel
 from typing_extensions import Annotated
 
 from kui.wsgi import (
@@ -245,3 +246,23 @@ def upload_file(file: Annotated[UploadFile, Body(...)]):
 
         resp = client.post("/", files={"file0": io.BytesIO(b"123")})
         assert resp.status_code == 422
+
+
+def test_parameters_nest_model():
+    app = Kui()
+
+    class User(BaseModel):
+        name: str
+        age: int
+
+    @app.router.http.post("/")
+    def create_user(user: Annotated[User, Body(...)]):
+        assert user.age >= 18
+        return user
+
+    with httpx.Client(app=app, base_url="http://testserver") as client:
+        resp = client.post("/", json={"user": {"name": "aber", "age": 18}})
+        assert resp.json() == {"name": "aber", "age": 18}
+
+        resp = client.post("/", json={"name": "aber", "age": 18})
+        assert resp.status_code == 422