diff --git a/end_to_end_tests/golden-record/my_test_api_client/api/tests/defaults_tests_defaults_post.py b/end_to_end_tests/golden-record/my_test_api_client/api/tests/defaults_tests_defaults_post.py
index 88e4421f4..e671e60ab 100644
--- a/end_to_end_tests/golden-record/my_test_api_client/api/tests/defaults_tests_defaults_post.py
+++ b/end_to_end_tests/golden-record/my_test_api_client/api/tests/defaults_tests_defaults_post.py
@@ -131,7 +131,7 @@ def _get_kwargs(
     }
 
 
-def _parse_response(*, response: httpx.Response) -> Optional[Union[None, HTTPValidationError]]:
+def _parse_response(*, response: httpx.Response) -> Optional[Union[HTTPValidationError, None]]:
     if response.status_code == 200:
         response_200 = None
 
@@ -143,7 +143,7 @@ def _parse_response(*, response: httpx.Response) -> Optional[Union[None, HTTPVal
     return None
 
 
-def _build_response(*, response: httpx.Response) -> Response[Union[None, HTTPValidationError]]:
+def _build_response(*, response: httpx.Response) -> Response[Union[HTTPValidationError, None]]:
     return Response(
         status_code=response.status_code,
         content=response.content,
@@ -172,7 +172,7 @@ def sync_detailed(
     required_model_prop: ModelWithUnionProperty,
     nullable_model_prop: Union[Unset, None, ModelWithUnionProperty] = UNSET,
     nullable_required_model_prop: Optional[ModelWithUnionProperty],
-) -> Response[Union[None, HTTPValidationError]]:
+) -> Response[Union[HTTPValidationError, None]]:
     kwargs = _get_kwargs(
         client=client,
         string_prop=string_prop,
@@ -221,7 +221,7 @@ def sync(
     required_model_prop: ModelWithUnionProperty,
     nullable_model_prop: Union[Unset, None, ModelWithUnionProperty] = UNSET,
     nullable_required_model_prop: Optional[ModelWithUnionProperty],
-) -> Optional[Union[None, HTTPValidationError]]:
+) -> Optional[Union[HTTPValidationError, None]]:
     """  """
 
     return sync_detailed(
@@ -266,7 +266,7 @@ async def asyncio_detailed(
     required_model_prop: ModelWithUnionProperty,
     nullable_model_prop: Union[Unset, None, ModelWithUnionProperty] = UNSET,
     nullable_required_model_prop: Optional[ModelWithUnionProperty],
-) -> Response[Union[None, HTTPValidationError]]:
+) -> Response[Union[HTTPValidationError, None]]:
     kwargs = _get_kwargs(
         client=client,
         string_prop=string_prop,
@@ -314,7 +314,7 @@ async def asyncio(
     required_model_prop: ModelWithUnionProperty,
     nullable_model_prop: Union[Unset, None, ModelWithUnionProperty] = UNSET,
     nullable_required_model_prop: Optional[ModelWithUnionProperty],
-) -> Optional[Union[None, HTTPValidationError]]:
+) -> Optional[Union[HTTPValidationError, None]]:
     """  """
 
     return (
diff --git a/end_to_end_tests/golden-record/my_test_api_client/api/tests/get_user_list.py b/end_to_end_tests/golden-record/my_test_api_client/api/tests/get_user_list.py
index ec2216810..095f4be9d 100644
--- a/end_to_end_tests/golden-record/my_test_api_client/api/tests/get_user_list.py
+++ b/end_to_end_tests/golden-record/my_test_api_client/api/tests/get_user_list.py
@@ -47,7 +47,7 @@ def _get_kwargs(
     }
 
 
-def _parse_response(*, response: httpx.Response) -> Optional[Union[List[AModel], HTTPValidationError]]:
+def _parse_response(*, response: httpx.Response) -> Optional[Union[HTTPValidationError, List[AModel]]]:
     if response.status_code == 200:
         response_200 = []
         _response_200 = response.json()
@@ -61,10 +61,14 @@ def _parse_response(*, response: httpx.Response) -> Optional[Union[List[AModel],
         response_422 = HTTPValidationError.from_dict(response.json())
 
         return response_422
+    if response.status_code == 423:
+        response_423 = HTTPValidationError.from_dict(response.json())
+
+        return response_423
     return None
 
 
-def _build_response(*, response: httpx.Response) -> Response[Union[List[AModel], HTTPValidationError]]:
+def _build_response(*, response: httpx.Response) -> Response[Union[HTTPValidationError, List[AModel]]]:
     return Response(
         status_code=response.status_code,
         content=response.content,
@@ -78,7 +82,7 @@ def sync_detailed(
     client: Client,
     an_enum_value: List[AnEnum],
     some_date: Union[datetime.date, datetime.datetime],
-) -> Response[Union[List[AModel], HTTPValidationError]]:
+) -> Response[Union[HTTPValidationError, List[AModel]]]:
     kwargs = _get_kwargs(
         client=client,
         an_enum_value=an_enum_value,
@@ -97,7 +101,7 @@ def sync(
     client: Client,
     an_enum_value: List[AnEnum],
     some_date: Union[datetime.date, datetime.datetime],
-) -> Optional[Union[List[AModel], HTTPValidationError]]:
+) -> Optional[Union[HTTPValidationError, List[AModel]]]:
     """ Get a list of things  """
 
     return sync_detailed(
@@ -112,7 +116,7 @@ async def asyncio_detailed(
     client: Client,
     an_enum_value: List[AnEnum],
     some_date: Union[datetime.date, datetime.datetime],
-) -> Response[Union[List[AModel], HTTPValidationError]]:
+) -> Response[Union[HTTPValidationError, List[AModel]]]:
     kwargs = _get_kwargs(
         client=client,
         an_enum_value=an_enum_value,
@@ -130,7 +134,7 @@ async def asyncio(
     client: Client,
     an_enum_value: List[AnEnum],
     some_date: Union[datetime.date, datetime.datetime],
-) -> Optional[Union[List[AModel], HTTPValidationError]]:
+) -> Optional[Union[HTTPValidationError, List[AModel]]]:
     """ Get a list of things  """
 
     return (
diff --git a/end_to_end_tests/golden-record/my_test_api_client/api/tests/int_enum_tests_int_enum_post.py b/end_to_end_tests/golden-record/my_test_api_client/api/tests/int_enum_tests_int_enum_post.py
index 7d14632c4..6691aecf0 100644
--- a/end_to_end_tests/golden-record/my_test_api_client/api/tests/int_enum_tests_int_enum_post.py
+++ b/end_to_end_tests/golden-record/my_test_api_client/api/tests/int_enum_tests_int_enum_post.py
@@ -34,7 +34,7 @@ def _get_kwargs(
     }
 
 
-def _parse_response(*, response: httpx.Response) -> Optional[Union[None, HTTPValidationError]]:
+def _parse_response(*, response: httpx.Response) -> Optional[Union[HTTPValidationError, None]]:
     if response.status_code == 200:
         response_200 = None
 
@@ -46,7 +46,7 @@ def _parse_response(*, response: httpx.Response) -> Optional[Union[None, HTTPVal
     return None
 
 
-def _build_response(*, response: httpx.Response) -> Response[Union[None, HTTPValidationError]]:
+def _build_response(*, response: httpx.Response) -> Response[Union[HTTPValidationError, None]]:
     return Response(
         status_code=response.status_code,
         content=response.content,
@@ -59,7 +59,7 @@ def sync_detailed(
     *,
     client: Client,
     int_enum: AnIntEnum,
-) -> Response[Union[None, HTTPValidationError]]:
+) -> Response[Union[HTTPValidationError, None]]:
     kwargs = _get_kwargs(
         client=client,
         int_enum=int_enum,
@@ -76,7 +76,7 @@ def sync(
     *,
     client: Client,
     int_enum: AnIntEnum,
-) -> Optional[Union[None, HTTPValidationError]]:
+) -> Optional[Union[HTTPValidationError, None]]:
     """  """
 
     return sync_detailed(
@@ -89,7 +89,7 @@ async def asyncio_detailed(
     *,
     client: Client,
     int_enum: AnIntEnum,
-) -> Response[Union[None, HTTPValidationError]]:
+) -> Response[Union[HTTPValidationError, None]]:
     kwargs = _get_kwargs(
         client=client,
         int_enum=int_enum,
@@ -105,7 +105,7 @@ async def asyncio(
     *,
     client: Client,
     int_enum: AnIntEnum,
-) -> Optional[Union[None, HTTPValidationError]]:
+) -> Optional[Union[HTTPValidationError, None]]:
     """  """
 
     return (
diff --git a/end_to_end_tests/golden-record/my_test_api_client/api/tests/json_body_tests_json_body_post.py b/end_to_end_tests/golden-record/my_test_api_client/api/tests/json_body_tests_json_body_post.py
index 074ab9d89..2c21e806e 100644
--- a/end_to_end_tests/golden-record/my_test_api_client/api/tests/json_body_tests_json_body_post.py
+++ b/end_to_end_tests/golden-record/my_test_api_client/api/tests/json_body_tests_json_body_post.py
@@ -29,7 +29,7 @@ def _get_kwargs(
     }
 
 
-def _parse_response(*, response: httpx.Response) -> Optional[Union[None, HTTPValidationError]]:
+def _parse_response(*, response: httpx.Response) -> Optional[Union[HTTPValidationError, None]]:
     if response.status_code == 200:
         response_200 = None
 
@@ -41,7 +41,7 @@ def _parse_response(*, response: httpx.Response) -> Optional[Union[None, HTTPVal
     return None
 
 
-def _build_response(*, response: httpx.Response) -> Response[Union[None, HTTPValidationError]]:
+def _build_response(*, response: httpx.Response) -> Response[Union[HTTPValidationError, None]]:
     return Response(
         status_code=response.status_code,
         content=response.content,
@@ -54,7 +54,7 @@ def sync_detailed(
     *,
     client: Client,
     json_body: AModel,
-) -> Response[Union[None, HTTPValidationError]]:
+) -> Response[Union[HTTPValidationError, None]]:
     kwargs = _get_kwargs(
         client=client,
         json_body=json_body,
@@ -71,7 +71,7 @@ def sync(
     *,
     client: Client,
     json_body: AModel,
-) -> Optional[Union[None, HTTPValidationError]]:
+) -> Optional[Union[HTTPValidationError, None]]:
     """ Try sending a JSON body  """
 
     return sync_detailed(
@@ -84,7 +84,7 @@ async def asyncio_detailed(
     *,
     client: Client,
     json_body: AModel,
-) -> Response[Union[None, HTTPValidationError]]:
+) -> Response[Union[HTTPValidationError, None]]:
     kwargs = _get_kwargs(
         client=client,
         json_body=json_body,
@@ -100,7 +100,7 @@ async def asyncio(
     *,
     client: Client,
     json_body: AModel,
-) -> Optional[Union[None, HTTPValidationError]]:
+) -> Optional[Union[HTTPValidationError, None]]:
     """ Try sending a JSON body  """
 
     return (
diff --git a/end_to_end_tests/golden-record/my_test_api_client/api/tests/optional_value_tests_optional_query_param.py b/end_to_end_tests/golden-record/my_test_api_client/api/tests/optional_value_tests_optional_query_param.py
index 64431ba2f..0b60a77a2 100644
--- a/end_to_end_tests/golden-record/my_test_api_client/api/tests/optional_value_tests_optional_query_param.py
+++ b/end_to_end_tests/golden-record/my_test_api_client/api/tests/optional_value_tests_optional_query_param.py
@@ -35,7 +35,7 @@ def _get_kwargs(
     }
 
 
-def _parse_response(*, response: httpx.Response) -> Optional[Union[None, HTTPValidationError]]:
+def _parse_response(*, response: httpx.Response) -> Optional[Union[HTTPValidationError, None]]:
     if response.status_code == 200:
         response_200 = None
 
@@ -47,7 +47,7 @@ def _parse_response(*, response: httpx.Response) -> Optional[Union[None, HTTPVal
     return None
 
 
-def _build_response(*, response: httpx.Response) -> Response[Union[None, HTTPValidationError]]:
+def _build_response(*, response: httpx.Response) -> Response[Union[HTTPValidationError, None]]:
     return Response(
         status_code=response.status_code,
         content=response.content,
@@ -60,7 +60,7 @@ def sync_detailed(
     *,
     client: Client,
     query_param: Union[Unset, List[str]] = UNSET,
-) -> Response[Union[None, HTTPValidationError]]:
+) -> Response[Union[HTTPValidationError, None]]:
     kwargs = _get_kwargs(
         client=client,
         query_param=query_param,
@@ -77,7 +77,7 @@ def sync(
     *,
     client: Client,
     query_param: Union[Unset, List[str]] = UNSET,
-) -> Optional[Union[None, HTTPValidationError]]:
+) -> Optional[Union[HTTPValidationError, None]]:
     """ Test optional query parameters """
 
     return sync_detailed(
@@ -90,7 +90,7 @@ async def asyncio_detailed(
     *,
     client: Client,
     query_param: Union[Unset, List[str]] = UNSET,
-) -> Response[Union[None, HTTPValidationError]]:
+) -> Response[Union[HTTPValidationError, None]]:
     kwargs = _get_kwargs(
         client=client,
         query_param=query_param,
@@ -106,7 +106,7 @@ async def asyncio(
     *,
     client: Client,
     query_param: Union[Unset, List[str]] = UNSET,
-) -> Optional[Union[None, HTTPValidationError]]:
+) -> Optional[Union[HTTPValidationError, None]]:
     """ Test optional query parameters """
 
     return (
diff --git a/end_to_end_tests/golden-record/my_test_api_client/api/tests/token_with_cookie_auth_token_with_cookie_get.py b/end_to_end_tests/golden-record/my_test_api_client/api/tests/token_with_cookie_auth_token_with_cookie_get.py
index c497a0b3a..1ca44278f 100644
--- a/end_to_end_tests/golden-record/my_test_api_client/api/tests/token_with_cookie_auth_token_with_cookie_get.py
+++ b/end_to_end_tests/golden-record/my_test_api_client/api/tests/token_with_cookie_auth_token_with_cookie_get.py
@@ -1,4 +1,4 @@
-from typing import Any, Dict, Optional, Union
+from typing import Any, Dict
 
 import httpx
 
@@ -26,24 +26,12 @@ def _get_kwargs(
     }
 
 
-def _parse_response(*, response: httpx.Response) -> Optional[Union[None, None]]:
-    if response.status_code == 200:
-        response_200 = None
-
-        return response_200
-    if response.status_code == 401:
-        response_401 = None
-
-        return response_401
-    return None
-
-
-def _build_response(*, response: httpx.Response) -> Response[Union[None, None]]:
+def _build_response(*, response: httpx.Response) -> Response[None]:
     return Response(
         status_code=response.status_code,
         content=response.content,
         headers=response.headers,
-        parsed=_parse_response(response=response),
+        parsed=None,
     )
 
 
@@ -51,7 +39,7 @@ def sync_detailed(
     *,
     client: Client,
     my_token: str,
-) -> Response[Union[None, None]]:
+) -> Response[None]:
     kwargs = _get_kwargs(
         client=client,
         my_token=my_token,
@@ -64,24 +52,11 @@ def sync_detailed(
     return _build_response(response=response)
 
 
-def sync(
-    *,
-    client: Client,
-    my_token: str,
-) -> Optional[Union[None, None]]:
-    """ Test optional cookie parameters """
-
-    return sync_detailed(
-        client=client,
-        my_token=my_token,
-    ).parsed
-
-
 async def asyncio_detailed(
     *,
     client: Client,
     my_token: str,
-) -> Response[Union[None, None]]:
+) -> Response[None]:
     kwargs = _get_kwargs(
         client=client,
         my_token=my_token,
@@ -91,18 +66,3 @@ async def asyncio_detailed(
         response = await _client.get(**kwargs)
 
     return _build_response(response=response)
-
-
-async def asyncio(
-    *,
-    client: Client,
-    my_token: str,
-) -> Optional[Union[None, None]]:
-    """ Test optional cookie parameters """
-
-    return (
-        await asyncio_detailed(
-            client=client,
-            my_token=my_token,
-        )
-    ).parsed
diff --git a/end_to_end_tests/golden-record/my_test_api_client/api/tests/upload_file_tests_upload_post.py b/end_to_end_tests/golden-record/my_test_api_client/api/tests/upload_file_tests_upload_post.py
index 705443d95..fb18e9f61 100644
--- a/end_to_end_tests/golden-record/my_test_api_client/api/tests/upload_file_tests_upload_post.py
+++ b/end_to_end_tests/golden-record/my_test_api_client/api/tests/upload_file_tests_upload_post.py
@@ -40,7 +40,7 @@ def _get_kwargs(
     }
 
 
-def _parse_response(*, response: httpx.Response) -> Optional[Union[None, HTTPValidationError]]:
+def _parse_response(*, response: httpx.Response) -> Optional[Union[HTTPValidationError, None]]:
     if response.status_code == 200:
         response_200 = None
 
@@ -52,7 +52,7 @@ def _parse_response(*, response: httpx.Response) -> Optional[Union[None, HTTPVal
     return None
 
 
-def _build_response(*, response: httpx.Response) -> Response[Union[None, HTTPValidationError]]:
+def _build_response(*, response: httpx.Response) -> Response[Union[HTTPValidationError, None]]:
     return Response(
         status_code=response.status_code,
         content=response.content,
@@ -66,7 +66,7 @@ def sync_detailed(
     client: Client,
     multipart_data: BodyUploadFileTestsUploadPost,
     keep_alive: Union[Unset, bool] = UNSET,
-) -> Response[Union[None, HTTPValidationError]]:
+) -> Response[Union[HTTPValidationError, None]]:
     kwargs = _get_kwargs(
         client=client,
         multipart_data=multipart_data,
@@ -85,7 +85,7 @@ def sync(
     client: Client,
     multipart_data: BodyUploadFileTestsUploadPost,
     keep_alive: Union[Unset, bool] = UNSET,
-) -> Optional[Union[None, HTTPValidationError]]:
+) -> Optional[Union[HTTPValidationError, None]]:
     """ Upload a file  """
 
     return sync_detailed(
@@ -100,7 +100,7 @@ async def asyncio_detailed(
     client: Client,
     multipart_data: BodyUploadFileTestsUploadPost,
     keep_alive: Union[Unset, bool] = UNSET,
-) -> Response[Union[None, HTTPValidationError]]:
+) -> Response[Union[HTTPValidationError, None]]:
     kwargs = _get_kwargs(
         client=client,
         multipart_data=multipart_data,
@@ -118,7 +118,7 @@ async def asyncio(
     client: Client,
     multipart_data: BodyUploadFileTestsUploadPost,
     keep_alive: Union[Unset, bool] = UNSET,
-) -> Optional[Union[None, HTTPValidationError]]:
+) -> Optional[Union[HTTPValidationError, None]]:
     """ Upload a file  """
 
     return (
diff --git a/end_to_end_tests/openapi.json b/end_to_end_tests/openapi.json
index 359419473..ed0de8918 100644
--- a/end_to_end_tests/openapi.json
+++ b/end_to_end_tests/openapi.json
@@ -70,6 +70,16 @@
                 }
               }
             }
+          },
+          "423": {
+            "description": "Validation Error",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/HTTPValidationError"
+                }
+              }
+            }
           }
         }
       }
diff --git a/openapi_python_client/parser/openapi.py b/openapi_python_client/parser/openapi.py
index 2361c3c66..283dd1948 100644
--- a/openapi_python_client/parser/openapi.py
+++ b/openapi_python_client/parser/openapi.py
@@ -265,6 +265,15 @@ def from_data(
 
         return result, schemas
 
+    def response_type(self) -> str:
+        """ Get the Python type of any response from this endpoint """
+        types = sorted({response.prop.get_type_string() for response in self.responses})
+        if len(types) == 0:
+            return "None"
+        if len(types) == 1:
+            return self.responses[0].prop.get_type_string()
+        return f"Union[{', '.join(types)}]"
+
 
 @dataclass
 class GeneratorData:
diff --git a/openapi_python_client/templates/endpoint_macros.py.jinja b/openapi_python_client/templates/endpoint_macros.py.jinja
index 705985aab..e822ff320 100644
--- a/openapi_python_client/templates/endpoint_macros.py.jinja
+++ b/openapi_python_client/templates/endpoint_macros.py.jinja
@@ -71,20 +71,6 @@ params = {k: v for k, v in params.items() if v is not UNSET and v is not None}
 {% endif %}
 {% endmacro %}
 
-{% macro return_type(endpoint) %}
-{% if endpoint.responses | length == 0 %}
-None
-{%- elif endpoint.responses | length == 1 %}
-{{ endpoint.responses[0].prop.get_type_string() }}
-{%- else %}
-Union[
-    {% for response in endpoint.responses %}
-    {{ response.prop.get_type_string() }}{{ "," if not loop.last }}
-    {% endfor %}
-]
-{%- endif %}
-{% endmacro %}
-
 {# The all the kwargs passed into an endpoint (and variants thereof)) #}
 {% macro arguments(endpoint) %}
 *,
diff --git a/openapi_python_client/templates/endpoint_module.py.jinja b/openapi_python_client/templates/endpoint_module.py.jinja
index 5b1c434bc..174d67b9d 100644
--- a/openapi_python_client/templates/endpoint_module.py.jinja
+++ b/openapi_python_client/templates/endpoint_module.py.jinja
@@ -10,9 +10,9 @@ from ...types import Response, UNSET{% if endpoint.multipart_body_reference %},
 {{ relative }}
 {% endfor %}
 
-{% from "endpoint_macros.py.jinja" import header_params, cookie_params, query_params, json_body, return_type, arguments, client, kwargs, parse_response %}
+{% from "endpoint_macros.py.jinja" import header_params, cookie_params, query_params, json_body, arguments, client, kwargs, parse_response %}
 
-{% set return_string = return_type(endpoint) %}
+{% set return_string = endpoint.response_type() %}
 {% set parsed_responses = (endpoint.responses | length > 0) and return_string != "None" %}
 
 def _get_kwargs(
diff --git a/tests/test_parser/test_openapi.py b/tests/test_parser/test_openapi.py
index 1bbaa3e6e..5f0ecdc90 100644
--- a/tests/test_parser/test_openapi.py
+++ b/tests/test_parser/test_openapi.py
@@ -1,3 +1,7 @@
+from unittest.mock import MagicMock
+
+import pytest
+
 import openapi_python_client.schema as oai
 from openapi_python_client import GeneratorError
 from openapi_python_client.parser.errors import ParseError
@@ -114,6 +118,19 @@ def test_from_dict_invalid_version(self, mocker):
 
 
 class TestEndpoint:
+    def make_endpoint(self):
+        from openapi_python_client.parser.openapi import Endpoint
+
+        return Endpoint(
+            path="path",
+            method="method",
+            description=None,
+            name="name",
+            requires_security=False,
+            tag="tag",
+            relative_imports={"import_3"},
+        )
+
     def test_parse_request_form_body(self, mocker):
         ref = mocker.MagicMock()
         body = oai.RequestBody.construct(
@@ -195,15 +212,7 @@ def test_add_body_no_data(self, mocker):
         from openapi_python_client.parser.openapi import Endpoint, Schemas
 
         parse_request_form_body = mocker.patch.object(Endpoint, "parse_request_form_body")
-        endpoint = Endpoint(
-            path="path",
-            method="method",
-            description=None,
-            name="name",
-            requires_security=False,
-            tag="tag",
-            relative_imports={"import_3"},
-        )
+        endpoint = self.make_endpoint()
         schemas = Schemas()
 
         Endpoint._add_body(endpoint=endpoint, data=oai.Operation.construct(), schemas=schemas)
@@ -217,15 +226,7 @@ def test_add_body_bad_data(self, mocker):
         parse_error = ParseError(data=mocker.MagicMock())
         other_schemas = mocker.MagicMock()
         mocker.patch.object(Endpoint, "parse_request_json_body", return_value=(parse_error, other_schemas))
-        endpoint = Endpoint(
-            path="path",
-            method="method",
-            description=None,
-            name="name",
-            requires_security=False,
-            tag="tag",
-            relative_imports={"import_3"},
-        )
+        endpoint = self.make_endpoint()
         request_body = mocker.MagicMock()
         schemas = Schemas()
 
@@ -263,15 +264,7 @@ def test_add_body_happy(self, mocker):
             f"{MODULE_NAME}.import_string_from_reference", side_effect=["import_1", "import_2"]
         )
 
-        endpoint = Endpoint(
-            path="path",
-            method="method",
-            description=None,
-            name="name",
-            requires_security=False,
-            tag="tag",
-            relative_imports={"import_3"},
-        )
+        endpoint = self.make_endpoint()
         initial_schemas = mocker.MagicMock()
 
         (endpoint, response_schemas) = Endpoint._add_body(
@@ -303,15 +296,7 @@ def test__add_responses_status_code_error(self, mocker):
         data = {
             "not_a_number": response_1_data,
         }
-        endpoint = Endpoint(
-            path="path",
-            method="method",
-            description=None,
-            name="name",
-            requires_security=False,
-            tag="tag",
-            relative_imports={"import_3"},
-        )
+        endpoint = self.make_endpoint()
         parse_error = ParseError(data=mocker.MagicMock())
         response_from_data = mocker.patch(f"{MODULE_NAME}.response_from_data", return_value=(parse_error, schemas))
 
@@ -333,15 +318,7 @@ def test__add_responses_error(self, mocker):
             "200": response_1_data,
             "404": response_2_data,
         }
-        endpoint = Endpoint(
-            path="path",
-            method="method",
-            description=None,
-            name="name",
-            requires_security=False,
-            tag="tag",
-            relative_imports={"import_3"},
-        )
+        endpoint = self.make_endpoint()
         parse_error = ParseError(data=mocker.MagicMock())
         response_from_data = mocker.patch(f"{MODULE_NAME}.response_from_data", return_value=(parse_error, schemas))
 
@@ -374,15 +351,7 @@ def test__add_responses(self, mocker):
             "200": response_1_data,
             "404": response_2_data,
         }
-        endpoint = Endpoint(
-            path="path",
-            method="method",
-            description=None,
-            name="name",
-            requires_security=False,
-            tag="tag",
-            relative_imports={"import_3"},
-        )
+        endpoint = self.make_endpoint()
         schemas = mocker.MagicMock()
         schemas_1 = mocker.MagicMock()
         schemas_2 = mocker.MagicMock()
@@ -420,14 +389,7 @@ def test__add_responses(self, mocker):
     def test__add_parameters_handles_no_params(self):
         from openapi_python_client.parser.openapi import Endpoint, Schemas
 
-        endpoint = Endpoint(
-            path="path",
-            method="method",
-            description=None,
-            name="name",
-            requires_security=False,
-            tag="tag",
-        )
+        endpoint = self.make_endpoint()
         schemas = Schemas()
         # Just checking there's no exception here
         assert Endpoint._add_parameters(endpoint=endpoint, data=oai.Operation.construct(), schemas=schemas) == (
@@ -438,14 +400,7 @@ def test__add_parameters_handles_no_params(self):
     def test__add_parameters_parse_error(self, mocker):
         from openapi_python_client.parser.openapi import Endpoint
 
-        endpoint = Endpoint(
-            path="path",
-            method="method",
-            description=None,
-            name="name",
-            requires_security=False,
-            tag="tag",
-        )
+        endpoint = self.make_endpoint()
         initial_schemas = mocker.MagicMock()
         parse_error = ParseError(data=mocker.MagicMock())
         property_schemas = mocker.MagicMock()
@@ -463,14 +418,7 @@ def test__add_parameters_parse_error(self, mocker):
     def test__add_parameters_fail_loudly_when_location_not_supported(self, mocker):
         from openapi_python_client.parser.openapi import Endpoint, Schemas
 
-        endpoint = Endpoint(
-            path="path",
-            method="method",
-            description=None,
-            name="name",
-            requires_security=False,
-            tag="tag",
-        )
+        endpoint = self.make_endpoint()
         parsed_schemas = mocker.MagicMock()
         mocker.patch(f"{MODULE_NAME}.property_from_data", return_value=(mocker.MagicMock(), parsed_schemas))
         param = oai.Parameter.construct(
@@ -487,15 +435,7 @@ def test__add_parameters_happy(self, mocker):
         from openapi_python_client.parser.openapi import Endpoint
         from openapi_python_client.parser.properties import Property
 
-        endpoint = Endpoint(
-            path="path",
-            method="method",
-            description=None,
-            name="name",
-            requires_security=False,
-            tag="tag",
-            relative_imports={"import_3"},
-        )
+        endpoint = self.make_endpoint()
         path_prop = mocker.MagicMock(autospec=Property)
         path_prop_import = mocker.MagicMock()
         path_prop.get_imports = mocker.MagicMock(return_value={path_prop_import})
@@ -731,6 +671,19 @@ def test_from_data_no_security(self, mocker):
             endpoint=_add_responses.return_value[0], data=data, schemas=_add_responses.return_value[1]
         )
 
+    @pytest.mark.parametrize(
+        "response_types, expected",
+        (([], "None"), (["Something"], "Something"), (["First", "Second", "Second"], "Union[First, Second]")),
+    )
+    def test_response_type(self, response_types, expected):
+        endpoint = self.make_endpoint()
+        for response_type in response_types:
+            mock_response = MagicMock()
+            mock_response.prop.get_type_string.return_value = response_type
+            endpoint.responses.append(mock_response)
+
+        assert endpoint.response_type() == expected
+
 
 class TestImportStringFromReference:
     def test_import_string_from_reference_no_prefix(self, mocker):