diff --git a/fastapi/applications.py b/fastapi/applications.py
index 340cabfc29..1c37f992fa 100644
--- a/fastapi/applications.py
+++ b/fastapi/applications.py
@@ -285,6 +285,7 @@ class FastAPI(Starlette):
                 """
             ),
         ] = None,
+        openapi_response_class: Type[JSONResponse] = JSONResponse,
         servers: Annotated[
             Optional[list[dict[str, Union[str, Any]]]],
             Doc(
@@ -864,6 +865,7 @@ class FastAPI(Starlette):
         self.license_info = license_info
         self.openapi_url = openapi_url
         self.openapi_tags = openapi_tags
+        self.openapi_response_class = openapi_response_class
         self.root_path_in_servers = root_path_in_servers
         self.docs_url = docs_url
         self.redoc_url = redoc_url
@@ -1090,7 +1092,7 @@ class FastAPI(Starlette):
                     if root_path and self.root_path_in_servers:
                         self.servers.insert(0, {"url": root_path})
                         server_urls.add(root_path)
-                return JSONResponse(self.openapi())
+                return self.openapi_response_class(self.openapi())
 
             self.add_route(self.openapi_url, openapi, include_in_schema=False)
         if self.openapi_url and self.docs_url: