diff --git a/README.md b/README.md
index 664bb3a..c8102b5 100644
--- a/README.md
+++ b/README.md
@@ -3,13 +3,13 @@ and Result from [returns](https://returns.readthedocs.io/en/latest/pages/result.
 so that both primary (200) and [additional](https://fastapi.tiangolo.com/advanced/additional-responses/)
 response types can be inferred from the path operation type signature.
 
-Install as user
+Install as user:
 ```bash
 pip install git+https://github.com/amacfie/fastapi_returns_inferring_router
 ```
 
 
-Install as developer
+Install as developer:
 ```bash
 pip install --editable .
 ```
diff --git a/fastapi_returns_inferring_router/__init__.py b/fastapi_returns_inferring_router/__init__.py
index bff7477..0aa12d0 100644
--- a/fastapi_returns_inferring_router/__init__.py
+++ b/fastapi_returns_inferring_router/__init__.py
@@ -3,9 +3,12 @@
 from typing import (TYPE_CHECKING, Any, Callable, Union, get_args, get_origin, get_type_hints)
 
 from fastapi import APIRouter
+from fastapi.datastructures import DefaultPlaceholder
 from fastapi.encoders import jsonable_encoder
 from fastapi.responses import JSONResponse
 from returns.result import Result, Success, Failure
+from semantic_version import Version
+import fastapi
 
 
 class ReturnsInferringRouter(APIRouter):
@@ -47,8 +50,7 @@ def new_endpoint(*args, **kwargs):
                 # pydantic maps None to something openapi doesn't recognize
                 if suc_type is None:
                     suc_type = Any
-                if kwargs.get("response_model") is None:
-                    kwargs["response_model"] = suc_type
+                kwargs["response_model"] = suc_type
 
                 if (
                     kwargs.get("responses") is None or
@@ -87,7 +89,7 @@ def new_endpoint(*args, **kwargs):
                             responses[code] = {"model": fail_model}
                     kwargs["responses"] = responses
 
-            else:
+            elif Version(fastapi.__version__) < Version("0.89.0"):
                 # same pydantic issue as above
                 if return_type is None:
                     return_type = Any
diff --git a/setup.cfg b/setup.cfg
index 2a80157..65cfd35 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -8,6 +8,7 @@ install_requires =
     fastapi==0.*
     returns==0.*
     build
+    semantic-version==2.*
     sphinx==4.*
     twine
 python_requires = >=3.10, <4