diff --git a/src/anthropic/_models.py b/src/anthropic/_models.py
index 00d787ca..ebaef994 100644
--- a/src/anthropic/_models.py
+++ b/src/anthropic/_models.py
@@ -121,6 +121,7 @@ def construct(
                 if PYDANTIC_V2:
                     _extra[key] = value
                 else:
+                    _fields_set.add(key)
                     fields_values[key] = value
 
         object.__setattr__(m, "__dict__", fields_values)
diff --git a/tests/test_client.py b/tests/test_client.py
index 56438da5..8cfa59ab 100644
--- a/tests/test_client.py
+++ b/tests/test_client.py
@@ -42,12 +42,12 @@ class TestAnthropic:
 
     @pytest.mark.respx(base_url=base_url)
     def test_raw_response(self, respx_mock: MockRouter) -> None:
-        respx_mock.post("/foo").mock(return_value=httpx.Response(200, json='{"foo": "bar"}'))
+        respx_mock.post("/foo").mock(return_value=httpx.Response(200, json={"foo": "bar"}))
 
         response = self.client.post("/foo", cast_to=httpx.Response)
         assert response.status_code == 200
         assert isinstance(response, httpx.Response)
-        assert response.json() == '{"foo": "bar"}'
+        assert response.json() == {"foo": "bar"}
 
     @pytest.mark.respx(base_url=base_url)
     def test_raw_response_for_binary(self, respx_mock: MockRouter) -> None:
@@ -58,7 +58,7 @@ def test_raw_response_for_binary(self, respx_mock: MockRouter) -> None:
         response = self.client.post("/foo", cast_to=httpx.Response)
         assert response.status_code == 200
         assert isinstance(response, httpx.Response)
-        assert response.json() == '{"foo": "bar"}'
+        assert response.json() == {"foo": "bar"}
 
     def test_copy(self) -> None:
         copied = self.client.copy()
@@ -669,12 +669,12 @@ class TestAsyncAnthropic:
     @pytest.mark.respx(base_url=base_url)
     @pytest.mark.asyncio
     async def test_raw_response(self, respx_mock: MockRouter) -> None:
-        respx_mock.post("/foo").mock(return_value=httpx.Response(200, json='{"foo": "bar"}'))
+        respx_mock.post("/foo").mock(return_value=httpx.Response(200, json={"foo": "bar"}))
 
         response = await self.client.post("/foo", cast_to=httpx.Response)
         assert response.status_code == 200
         assert isinstance(response, httpx.Response)
-        assert response.json() == '{"foo": "bar"}'
+        assert response.json() == {"foo": "bar"}
 
     @pytest.mark.respx(base_url=base_url)
     @pytest.mark.asyncio
@@ -686,7 +686,7 @@ async def test_raw_response_for_binary(self, respx_mock: MockRouter) -> None:
         response = await self.client.post("/foo", cast_to=httpx.Response)
         assert response.status_code == 200
         assert isinstance(response, httpx.Response)
-        assert response.json() == '{"foo": "bar"}'
+        assert response.json() == {"foo": "bar"}
 
     def test_copy(self) -> None:
         copied = self.client.copy()
diff --git a/tests/test_transform.py b/tests/test_transform.py
index 8e1d4724..5f9abd21 100644
--- a/tests/test_transform.py
+++ b/tests/test_transform.py
@@ -7,6 +7,7 @@
 import pytest
 
 from anthropic._utils import PropertyInfo, transform, parse_datetime
+from anthropic._compat import PYDANTIC_V2
 from anthropic._models import BaseModel
 
 
@@ -210,14 +211,20 @@ def test_pydantic_unknown_field() -> None:
 
 def test_pydantic_mismatched_types() -> None:
     model = MyModel.construct(foo=True)
-    with pytest.warns(UserWarning):
+    if PYDANTIC_V2:
+        with pytest.warns(UserWarning):
+            params = transform(model, Any)
+    else:
         params = transform(model, Any)
     assert params == {"foo": True}
 
 
 def test_pydantic_mismatched_object_type() -> None:
     model = MyModel.construct(foo=MyModel.construct(hello="world"))
-    with pytest.warns(UserWarning):
+    if PYDANTIC_V2:
+        with pytest.warns(UserWarning):
+            params = transform(model, Any)
+    else:
         params = transform(model, Any)
     assert params == {"foo": {"hello": "world"}}